Many of the time functions had grown overly complex in order to
handle kernel compatibility issues. However, as of Linux 2.6.26
all the required functionality is available. This allows us to
retire numerous configure checks and greatly simplify the time
compatibility wrappers.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The fls64() function has been available since Linux 2.6.16 and
it should be used to implemented highbit64(). This allows us
to provide an optimized implementation and simplify the code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Support for the CTL_UNNUMBERED sysctl interface was removed in
Linux 2.6.19. There is no longer any reason to maintain this
compatibility code. There also issue any reason to keep around
the CTL_NAME macro and helpers so they have been retired.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The register_sysctl() interface has been stable since Linux 2.6.21.
There is no longer a need to maintain compatibility code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
There is no longer a need to wrap this because utsname() is provided
by the kernel and can be called directly. This will require a small
change in the ZFS code because utsname is expected to be a global
structure and not a function.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The generic SPL cache shrinkers make the assumption that the
caches only contain VFS cache data and therefore should be scaled
based on vfs_cache_pressure. This is not strictly true and it
should not be assumed.
Removing this tuning should not have any impact on the stock
behavior because vfs_cache_pressure=100 by default. This means
that no scaling will take place.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Since the Linux 2.6.29 kernel all mutexes have been adaptive mutexs.
There is no longer any point in keeping this code so it is being
removed to simplify the code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Apply the license specified in the META file to ensure the
compatibility checks are all performed consistently.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The smp_mb__{before,after}_clear_bit functions have been renamed
smp_mb__{before,after}_atomic. Rather than adding a compatibility
function to handle this the code has been updated to use smp_wmb().
This has the advantage of being a stable functionally equivalent
interface. On many architectures smp_mb__after_clear_bit() expands
to smp_wmb(). Others might be able to do something slightly more
efficient but this will be safe and correct on all of them.
Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#386
zfsonlinux/spl#bcb15891ab394e11615eee08bba1fd85ac32e158 implemented
Linux 3.6+ support by adding duplicate vn_rename and vn_remove
functions. The new ones were cleaner, but the duplicate functions made
the codebase less maintainable. This adds some compatibility shims that
allow us to retire the older vn_rename and vn_remove in favor of the new
ones on old kernels. The result is a net 143 line reduction in lines of
code and a cleaner codebase.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#370
Linux kernel 3.17 removes the action function argument from
wait_on_bit(). Add autoconf test and compatibility macro to support
the new interface.
The former "wait_on_bit" interface required an 'action' function to
be provided which does the actual waiting. There were over 20 such
functions in the kernel, many of them identical, though most cases
can be satisfied by one of just two functions: one which uses
io_schedule() and one which just uses schedule(). This API change
was made to consolidate all of those redundant wait functions.
References: torvalds/linux@7431620
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#378
For small objects the Linux slab allocator should be used to make the most
efficient use of the memory. However, large objects are not supported by
the Linux slab and therefore the SPL implementation is preferred. A cutoff
of 16K was determined to be optimal for architectures using 4K pages.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: DHE <git@dehacked.net>
Issue #356Closes#379
Reinstate the correct default behavior of returning the number of objects
in the cache for reclaim. This behavior was disabled in recent releases
to do occasional reports of spinning in shrink_slabs(). Those issues have
been resolved and can no longer can be reproduced. See commit 376dc35.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: DHE <git@dehacked.net>
Issue #358Closes#379
Added highbit64() and howmany() which are used in recent upstream
code. Both highbit() and highbit64() should at some point be
re-factored to use the optimized fls() and fls64() functions.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#363
There have been issues in the past where excessive debug logging
to the console has resulted in significant performance impacts.
In the vast majority of these cases only a few stack traces are
required to diagnose the issue. Therefore, stack traces dumped to
the console will now we limited to 5 every 60s.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Closes#374
Spl's debugging and assertion macros macro used the typical do/while(0)
form for if/else friendliness, however, this limits their use in contexts
where a do loop is not valid; such as within another multi-statement
style macro.
The following macros have been converted to not use do/while(0):
PANIC, ASSERT, ASSERTF, VERIFY, VERIFY3_IMPL
PANIC has been converted to a wrapper around the new spl_PANIC() function.
The other macros have been converted to use the "&&" operator for the
branch-predicition conditional and also to use spl_PANIC().
The __ASSERT() macro was not touched. It is only used by the debugging
infrastructure and that code, including this macro, will be retired when
the tracepoint patches are merged.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#367
The correct behavior for all registered shrinkers is to return the
number of objects in their cache. In theory this allows the Linux
VM to balance memory reclaim across all registered caches.
In commit b9b3715 this behavior was disabled in favor of returning
-1 which notifies the VM that no additional objects are available
for reclaim. This was done as a workaround to resolve thrashing
in shrink_slabs() which could occur when memory was low and numerous
core where in reclaim. Unfortunately, this has been observed to
increase the likelihood of OOM events when SPL slab consumers are
responsible for consuming the majority of memory.
Therefore, this patch makes this behavior tunable. Setting the
spl_kmem_cache_reclaim module option to 0x1 will result in the
shrinker only being called once. This is the default behavior.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Closes#358
For small objects the Linux slab allocator has several advantages
over its counterpart in the SPL. These include:
1) It is more memory-efficient and packs objects more tightly.
2) It is continually tuned to maximize performance.
Therefore it makes sense to layer the SPLs slab allocator on top
of the Linux slab allocator. This allows us to leverage the
advantages above while preserving the Illumos semantics we depend
on. However, there are some things we need to be careful of:
1) The Linux slab allocator was never designed to work well with
large objects. Because the SPL slab must still handle this use
case a cut off limit was added to transition from Linux slab
backed objects to kmem or vmem backed slabs.
spl_kmem_cache_slab_limit - Objects less than or equal to this
size in bytes will be backed by the Linux slab. By default
this value is zero which disables the Linux slab functionality.
Reasonable values for this cut off limit are in the range of
4096-16386 bytes.
spl_kmem_cache_kmem_limit - Objects less than or equal to this
size in bytes will be backed by a kmem slab. Objects over this
size will be vmem backed instead. This value defaults to
1/8 a page, or 512 bytes on an x86_64 architecture.
2) Be aware that using the Linux slab may inadvertently introduce
new deadlocks. Care has been taken previously to ensure that
all allocations which occur in the write path use GFP_NOIO.
However, there may be internal allocations performed in the
Linux slab which do not honor these flags. If this is the case
a deadlock may occur.
The path forward is definitely to start relying on the Linux slab.
But for that to happen we need to start building confidence that
there aren't any unexpected surprises lurking for us. And ideally
need to move completely away from using the SPLs slab for large
memory allocations. This patch is a first step.
NOTES:
1) The KMC_NOMAGAZINE flag was leveraged to support the Linux slab
backed caches but it is not supported for kmem/vmem backed caches.
2) Regardless of the spl_kmem_cache_*_limit settings a cache may
be explicitly set to a given type by passed the KMC_KMEM,
KMC_VMEM, or KMC_SLAB flags during cache creation.
3) The constructors, destructors, and reclaim callbacks are all
functional and will be called regardless of the cache type.
4) KMC_SLAB caches will not appear in /proc/spl/kmem/slab due to
the issues involved in presenting correct object accounting.
Instead they will appear in /proc/slabinfo under the same names.
5) Several kmem SPLAT tests needed to be fixed because they relied
incorrectly on internal kmem slab accounting. With the updated
test cases all the SPLAT tests pass as expected.
6) An autoconf test was added to ensure that the __GFP_COMP flag
was correctly added to the default flags used when allocating
a slab. This is required to ensure all pages in higher order
slabs are properly refcounted, see ae16ed9.
7) When using the SLUB allocator there is no need to attempt to
set the __GFP_COMP flag. This has been the default behavior
for the SLUB since Linux 2.6.25.
8) When using the SLUB it may be desirable to set the slub_nomerge
kernel parameter to prevent caches from being merged.
Original-patch-by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: DHE <git@dehacked.net>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Closes#356
Detect the updated vfs_rename() interface and call it with an
extra flags argument.
References:
torvalds/linux@520c8b1
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #355
The problem is described in commit aeeb4e0c0a.
However, instead of disabling the binding to CPU altogether we just keep the
last CPU index across calls to taskq_create() and thus achieve even
distribution of the taskq threads across all available CPUs.
The implementation based on assumption that task queues initialization
performed in serial manner.
Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
Signed-off-by: Andrey Vesnovaty <andreyv@infinidat.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#336
When using __get_free_pages to get high order memory, only the first page's
_count will set to 1, other's will be 0. When an internal page get passed into
rbd, it will eventully go into tcp_sendpage. There, it will be called with
get_page and put_page, and get freed erroneously when _count jump back to 0.
The solution to this problem is to use compound page. All pages in a
high order compound page share a single _count. So get_page and put_page in
tcp_sendpage will not cause _count jump to 0.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#251
This behavior is more consistent with the way memory reclaim
is expected to work under Linux.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#349
By default maximal number of objects in slab can't exceed (16*2 - 1) and slab
size can't exceed 32M.
Today's high end servers having couple hundreds of RAM available for ARC may
run into a trouble with virtual memory because of the restriction mentioned
above.
Problem:
Reasons for very high number of virtual memory allocations:
* Real slab size very small relative to the size of the entire RAM
* Slabs allocated on virtual memory and fill entire ARC
The result is very high number of allocated virtual memory ranges (hundreds of
ranges). When virtual memory subsystem manages high number of ranges its
performance become so poor that it freezes from time to time.
Solution:
Number of objects per slab should be increased taking into account maximal
slab size which can also be increased if needed.
Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#337
There is plenty of compatibility code for a hw_hostid
that isn't used by anything. At the same time, there are apparently
issues with the current hostid logic. coredumb in #zfsonlinux on
freenode reported that Fedora 17 changes its hostid on every boot, which
required force importing his pool. A suggestion by wca was to adopt
FreeBSD's behavior, where it treats hostid as zero if /etc/hostid does
not exist
Adopting FreeBSD's behavior permits us to eliminate plenty of code,
including a userland helper that invokes the system's hostid as a
fallback.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#224
The kernel's kthread_create() function is defined as "..." and there is
no va_list variant at the moment. The task name is pre-formatted into
a local buffer and passed to kthread_create() with fixed arguments.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#347
The function was defined as a static inline with variable arguments
which causes gcc to generate errors on some distros.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#346
Provide spl_kthread_create() as a wrapper to the kernel's kthread_create()
to provide pre-3.13 semantics. Re-try if the call is interrupted or if it
would have returned -ENOMEM. Otherwise return NULL.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#339
Due to certain assumptions made in the the cred:groupmember test it
could result in false positives when run on specific distributions.
This was solely a bug in the test case and not in the groupmember()
function which the test case was validating.
To prevent future false positives the test case has been rewritten
to be both more rigerous and to make fewer assumptions about the
system.
Minor style cleanup was done to cr_groups_search() and groupmember()
functions.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When this code was written it appears to have been assumed that
every taskq would have a large number of threads. In this case
it would make sense to attempt to evenly bind the threads over
all available CPUs. However, it failed to consider that creating
taskqs with a small number of threads will cause the CPUs with
lower ids become over-subscribed.
For this reason the kthread_bind() call is being removed and
we're leaving the kernel to schedule these threads as it sees fit.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#325
Use the standard Linux MODULE_VERSION macro to expose the installed
spl and splat module versions. This will also automatically add a
checksum of the .c files and headers in "srcversion". See:
/sys/module/spl/version
/sys/module/spl/srcversion
/sys/module/splat/version
/sys/module/splat/srcversion
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/zfs#1923
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This check was originally added for SLES10, a093c6a, to check for
a 'struct vfsmount *' argument which they added. However, since
SLES10 is based on a 2.6.16 kernel which is no longer supported
this functionality was dropped. The checks were refactored to
support Linux 3.13 without concern for historical versions.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#312
GCC 4.8.1 complained about an unused flags variable when building
against Linux 2.6.26.8:
/var/tmp/portage/sys-kernel/spl-9999/work/spl-9999/module/spl/../../module/spl/spl-condvar.c:
In function ‘__cv_init’:
/var/tmp/portage/sys-kernel/spl-9999/work/spl-9999/module/spl/../../module/spl/spl-condvar.c:39:6:
error: variable ‘flags’ set but not used
[-Werror=unused-but-set-variable]
int flags = KM_SLEEP;
^
cc1: all warnings being treated as errors
Additionally, the superfluous code uses a preempt_count variable that is
no longer available on Linux 3.13. Deleting the unnecessary code fixes a
Linux 3.13 compatibility issue.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#312
Needed for Illumos #3582. This interface is supposed to support
a variable-resolution timeout with nanosecond granularity. This
implementation rounds up to microsecond resolution, as nanosecond-
precision timing is rarely needed for real-world performance
tuning and may incur unnecessary busy-waiting. usleep_range() is
used if available, otherwise udelay() or msleep() are used
depending on the length of the delay interval.
Add flags from sys/callo.h as these are used to control the behavior of
cv_timedwait_hires(). Specifically,
CALLOUT_FLAG_ABSOLUTE
Normally, the expiration passed to the timeout API functions is
an expiration interval. If this flag is specified, then it is
interpreted as the expiration time itself.
CALLOUT_FLAG_ROUNDUP
Roundup the expiration time to the next resolution boundary. If this
flag is not specified, the expiration time is rounded down.
References:
https://www.illumos.org/issues/3582illumos/illumos-gate@0689f76
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#304
These kstat interfaces are required to port
"Illumos #3537 want pool io kstats" to ZFS on Linux.
kstat_waitq_enter()
kstat_waitq_exit()
kstat_runq_enter()
kstat_runq_exit()
Additionally, zero out the ks_data buffer in __kstat_create() so
that the kstat_io_t counters are initialized to zero.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
While porting Illumos #3537 I found that ks_lock member of kstat_t
structure is different between Illumos and SPL. It is a pointer to
the kmutex_t in Illumos, but the mutex lock itself in SPL.
Apparently Illumos kstat API allows consumer to override the lock
if required. With SPL implementation it is not possible anymore.
Things were alright until the first attempt to actually override
the lock. Porting of Illumos #3537 introduced such code for the
first time.
In order to provide the Solaris/Illumos like functionality we:
1. convert ks_lock to "kmutex_t *ks_lock"
2. create a new field "kmutex_t ks_private_lock"
3. On kstat_create() ks_lock = &ks_private_lock
Thus if consumer doesn't care we still have our internal lock in use.
If, however, consumer does care she has a chance to set ks_lock to
anything else before calling kstat_install().
The rest of the code will use ks_lock regardless of its origin.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #286
This reverts commit dba79fcbf2 in
favor of using the generic KSTAT_TYPE_RAW callbacks. The advantage
of this approach is that arbitrary types can be added without the
need to add them to the SPL.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #296
The current implementation for displaying kstats of type KSTAT_TYPE_RAW
is rather crude. This patch attempts to enhance this handling by
allowing a kstat user to register formatting callbacks which can
optionally be used.
The callbacks allow the user to implement functions for interpreting
their data and transposing it into a character buffer. This buffer,
containing a string representation of the raw data, is then be displayed
through the current /proc textual interface.
Additionally the kstats are made writable because it's now possible
to provide a useful handler via the existing ks_update() interface.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #296
It was observed that spl_kmem_cache_alloc() uses local_irq_save()
and saves the interrupt state in a local variable. This would
normally be fine except that spl_kmem_cache_alloc() calls
spl_cache_refill() which re-enables interrupts. It is then
possible that while interrupts are enabled the process is
rescheduled to a different cpu before being disable again.
This could result in us restoring the saved interrupt state
from one cpu to another.
What the consequences of this are aren't perfectly clear, but
this is clearly a bug and it has the potential to cause issues.
The code has been updated to just use local_irq_enable() and
local_irq_disable() to avoid this.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
current_kernel_time() is used by the SPLAT, but it is not meant for
performance measurement. We modify the SPLAT to use getnstimeofday(),
which is equivalent to the gethrestime() function on Solaris.
Additionally, we update gethrestime() to invoke getnstimeofday().
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#279
When CONFIG_UIDGID_STRICT_TYPE_CHECKS is enabled uid_t/git_t are
replaced by kuid_t/kgid_t, which are structures instead of integral
types. This causes any code that uses an integral type to fail to build.
The User Namespace functionality introduced in Linux 3.8 requires
CONFIG_UIDGID_STRICT_TYPE_CHECKS, so we could not build against any
kernel that supported it.
We resolve this by converting between the new kuid_t/kgid_t structures
and the original uid_t/gid_t types.
Original-patch-by: DHE
Rewrite-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#260
The PaX team started constifying `struct ctl_table` as of their Linux
3.8.0 patchset. This lead to zfsonlinux/spl#225 and Gentoo bug #463012.
While investigating our options, I learned that there is a preprocessor
directive called CONSTIFY_PLUGIN that we can use to detect the presence
of the PaX changes and adjust the code accordingly.
The PaX Team had suggested adopting ctl_table_no_const, but supporting
older kernels required declaring that whenever the CONSTIFY_PLUGIN was
set. Future compiler changes could potentially cause that to break in
the presence of -Werror, so instead we define our own spl_ctl_table
typdef and use that. This should be compatible with all PaX kernels.
This introduces a Linux kernel version number check to prevent a build
failure on versions of the PaX GCC plugin that existed for kernels
before Linux 3.8.0. Affected versions of the PaX plugin will trigger a
compiler error when they see no_const cast on a non-constified
structure. Ordinarily, we would need an autotools check to catch that.
However, it is safe to do a kernel version check instead of an autotools
check in this specific instance because the affected versions of the PaX
GCC plugin only exist for Linux kernels before 3.8.0 and the
constification of `struct ctl_table` by the PaX developers only occurs
in Linux 3.8.0 and later.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#225
The current code contains a race condition that triggers when bit 2 in
spl.spl_kmem_cache_expire is set, spl_kmem_cache_reap_now() is invoked
and another thread is concurrently accessing its magazine.
spl_kmem_cache_reap_now() currently invokes spl_cache_flush() on each
magazine in the same thread when bit 2 in spl.spl_kmem_cache_expire is
set. This is unsafe because there is one magazine per CPU and the
magazines are lockless, so it is impossible to guarentee that another
CPU is not using its magazine when this function is called.
The solution is to only touch the local CPU's magazine and leave other
CPU's magazines to other CPUs.
Reported-by: DHE
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#274
num_physpages was removed by
torvalds/linux@cfa11e08ed, so lets replace
it with totalram_pages.
This is a bug fix as much as it is a compatibility fix because
num_physpages did not reflect the number of pages actually available to
the kernel:
http://lkml.indiana.edu/hypermail/linux/kernel/0908.2/01001.html
Also, there are known issues with memory calculations when ZFS is in a
Xen dom0. There is a chance that using totalram_pages could resolve
them. This conjecture is untested at the time of writing.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#273
Because spl_slab_size() was always returning -ENOSPC for caches of
type KMC_OFFSLAB the cache could never be created. Additionally
the slab size is rounded up to a page which is what kv_alloc()
expects. The kv_alloc() code will minimally allocate a page,
in the KMC_OFFSLAB case this could be reduced.
The basic regression tests kmem:slab_small, kmem:slab_large,
and kmem:slab_align regression were updated to test KMC_OFFSLAB.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ying Zhu <casualfisher@gmail.com>
Closes#266
It has been observed that it's possible to get in a state where
shrink_slabs() will spin repeated invoking the generic kmem cache
shrinker. It fails to detect it's not making forward progress
reclaiming from the cache and doesn't give up. To ensure this
never occurs we unconditionally return -1 after reclaiming what
we can.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closeszfsonlinux/zfs#1276Closeszfsonlinux/zfs#1598Closeszfsonlinux/zfs#1432
This allows us to get nanosecond resolution. It also means
we use the same time source as utimensat(now) etc.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#255
Commit 5c7a036 correctly relocated the creation of a taskq
and the registraction of the kmem_cache_shrinker after the
initialization of the kmem tracking code. However, the
cleanup of these structures was not done before the leak
checks in spl_kmem_fini(). This resulted in an incorrect
'kmem leaked' warning even though there was no actual leak.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/zfs#1569
This code has gotten something stale and no longer builds cleanly
against modern kernels. The two issues addressed here are as
follows:
* The hlist_*_rcu interfaces in the kernel have been relatively
unstable. Since this isn't performance critical code just use
the long standing hlist_* variants.
* In older kernels the hash_ptr() function takes a 'void *' but
in newer kernels it expects a 'const void *'. To silence the
compiler warnings about this explicitly cast it to a 'void *'.
The memset function is a similar case but it always expects
a 'void *'.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#256
Linux kernel commit torvalds/linux#59d8053f moved the definition of
struct proc_dir_entry from include/linux/proc_fs.h to the private
header fs/proc/internal.h. The SPL relied on that to map Solaris'
kstat to entries in /proc/spl/kstat.
Since the proc_dir_entry structure is now private the only safe
thing to do is wrap the opaque proc handle with our own structure.
This actually ends up simplify the code and is good because it
moves us away from depending on implementation details of /proc.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Linux kernel commit torvalds/linux@d9dda78b renamed PDE() to
PDE_DATA(). To handle this detect the prefered interface
and define a PDE_DATA() wrapper for consistency.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #257
Re-order initialization in spl_kmem_init to allow for kmem tracing
to work. The spl_kmem_init function calls taskq_create prior to
initializing the tracking (calling spl_kmem_init_tracking). Since
taskq_create uses kmem_alloc, NULL dereferences occur because the
global kmem_list hasn't had its next & prev pointers initialized yet.
This commit moves the calls to spl_kmem_init_tracking earlier in the
spl_kmem_init function in order that the subsequent kmem_alloc calls
(by taskq_create) work properly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#243
The existing taskq_wait_id() function can incorrectly block
indefinitely. Reimplement it more simply using wait_event()
in a similar fashion to taskq_wait_all().
This flaw was uncovered in the context of moving vn_rdwr() to
a taskq. Previously taskq_wait_id() had no consumers outside
the SPLAT task framework which is why the issue went unnoticed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Calling cond_resched() after each object is freed and then after each
slab is freed can cause slabs of objects to live for excessive periods
of time following reclaimation. This interferes with the kernel's own
memory management when called from kswapd and can cause direct reclaim
to occur in response to memory pressure that should have been resolved.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
torvalds/linux@b67bfe0d42 changed
hlist_for_each_entry{,_rcu} to take 3 arguments instead of 4. We handle
this by switching to hlist_for_each{,_rcu}, which works across all
supported kernels.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This was a suggestion that Brian Behlendorf made when reviewing an early
pull request for Linux 3.9 support. This commit was made intentionally
easy to revert should we ever have a reason to reintroduce support for
older kernels.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
torvalds/linux@dcf787f391 enforces
const-correctness in passing struct path *.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The function prototype of vfs_getattr previoulsy took struct vfsmount *
and struct dentry * as arguments. These would always be defined together
in a struct path *.
torvalds/linux@3dadecce20 modified
vfs_getattr to take struct path * is taken as an argument instead.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
torvalds/linux@182be68478 removed the
preprocessor definition for f_vfsmnt. The ability to access the
mountpoint via ->f_path.mnt has been stable for a long time, so we
switch to that.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Update links to refer to the official ZFS on Linux website instead of
@behlendorf's personal fork on github.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Long ago infrastructure was added to the SPL to keep an internal
debug log of the last few seconds of activity. This was helpful
during the early development, but these days it is no longer
needed. I haven't had to resort to this debug buffer to resolve
an issue for several years now.
Today better more generic tools like systemtap and ftrace have
evolved to the point where they can be used for this purpose.
Along with the stack trace dumped to the system console, and in
rare cases a crash dump we almost always have the debug we need.
Therefore, I'm disabling the code which automatically dumps
this log to disk during an assertion except for the case where
spl_debug_panic_on_bug is set (disabled by default).
This should be viewed as a first step towards either.
a) Retiring this infrastructure and complexity entirely, or
b) Integrating this logging more properly with ftrace.
As part of this change I'm also removing from the packages the
undocumented spl utility which is used to decode the binary logs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The tsd_exit() and tsd_destroy() functions remove entries from
hash bins without taking the hash bin lock. They do take the
table lock, but tsd_get() and tsd_set() only take the hash bin
lock to allow for maximum concurency.
The result is that while tsd_get() and tsd_set() are traversing
the hash bin list it can be modified by another thread in which
happens to hash to the same value. To avoid this add the needed
locking to tsd_exit() and tsd_destroy().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#174
Cache aging was implemented because it was part of the default Solaris
kmem_cache behavior. The idea is that per-cpu objects which haven't been
accessed in several seconds should be returned to the cache. On the other
hand Linux slabs never move objects back to the slabs unless there is
memory pressure on the system.
This behavior is now configurable through the 'spl_kmem_cache_expire'
module option. The value is a bit mask with the following meaning.
0x1 - Solaris style cache aging eviction is enabled.
0x2 - Linux style low memory eviction is enabled.
Both methods may be safely enabled simultaneously, but by default
both are disabled. It has never been clear if the kmem cache aging
(which has been around from day one) actually does any good. It has
however been the source of numerous bugs so I wouldn't mind retiring
it entirely.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes zfsonlinux/zfs#1227
Closes#210
This functionality is no longer required by ZFS, see commit
zfsonlinux/zfs@7b3e34ba5a.
Since there are no other consumers, and because it adds
additional autoconf complexity which must be maintained
the spl_invalidate_inodes() function has been removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#795
Commit a10287e00d slightly reworked
the slab ageing code such that it is no longer dependent on the
Linux delayed work queue interfaces.
This was good for portability and performance, but it requires us
to use the on_each_cpu() function to execute the spl_magazine_age()
function. That means that the function is now executing in interrupt
context whereas before it was scheduled in normal process context.
And that means we need to be slightly more careful about the locking
in the interrupt handler.
With the reworked code it's possible that we'll be holding the
skc->skc_lock and be interrupted to handle the spl_magazine_age()
IRQ. This will result in a deadlock and soft lockup errors unless
we're careful to detect the contention and avoid taking the lock in
the interupt handler. So that's what this patch does.
Alternately, (and slightly more conventionally) we could have used
spin_lock_irqsave() to prevent this race entirely but I'd perfer to
avoid disabling interrupts as much as possible due to performance
concerns. There is absolutely no penalty for us not aging objects
out of the magazine due to contention.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Closeszfsonlinux/zfs#1193
As of Linux 3.4 the UMH_WAIT_* constants were renumbered. In
particular, the meaning of "1" changed from UMH_WAIT_PROC (wait for
process to complete), to UMH_WAIT_EXEC (wait for the exec, but not the
process). A number of call sites used the number 1 instead of the
constant name, so the behavior was not as expected on kernels with
this change.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In the upstream kernel the FALLOC_FL_PUNCH_HOLE #define was
introduced after the fallocate() function was moved from the
inode_operations to the file_operations structure. Therefore,
the SPL code assumed that if FALLOC_FL_PUNCH_HOLE was defined
it was safe to use f_ops->fallocate().
Unfortunately, the RHEL6.4 kernel has only backported the
FALLOC_FL_PUNCH_HOLE #define and not the fallocate() change.
To address this compatibility issue the spl_filp_fallocate()
helper function was added to properly detect which interface
is available.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Under Linux when a task is waiting on I/O it should call the
io_schedule() function for proper accounting. The Solaris
cv_wait() function provides no way to specify what the cv
is waiting on therefore cv_wait_io() is introduced.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#206
Due to I/O buffering the helper may return successfully before
the proc handler has a chance to execute. To catch this case
wait up to 1 second to verify spl_kallsyms_lookup_name_fn was
updated to a non SYMBOL_POISON value.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/zfs#699Closeszfsonlinux/zfs#859
Shift the asynchronous allocations over to use the taskq interfaces.
This allows us to abandon the kernels delayed work queue interface
and all the compatibility code it requires.
This code never actually used the delay functionality it was just
done this way to leverage the existing compatibility code. All that
is required is a thread context to perform the allocation in. The
only thing clever in this change is that we take advantage of the
preallocated task queue entries to avoid a memory allocation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Shift the cache and magazine ageing functionality over to the new
delayed taskq interfaces. This allows us to abandon the kernels
delayed work queue interface and all the compatibility code it
requires.
However, the delayed taskq interface does not allow us to schedule
a task for a specfic cpu so the ageing code was slightly reworked.
The magazine ageing delay has been directly linked to the cache
ageing function. The spl_cache_age() function invokes on_each_cpu()
in order to run spl_magazine_age() on each cpu. It then blocks
waiting for them to complete and promptly reclaims any free slabs.
When restructing the code wasn't the primary goal I think the
new code is far more understable and maintainable. It also should
help minimize magazine thrashing because free slabs are immediately
released after the magazine is aged.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When this code was originally written I went overboard and allowed
for the possibility of creating a cache in an atomic context. In
practice there are no callers which ever do this. This makes sense
since a cache is by design a long lived data structure.
To prevent abuse of this function going forward I'm removing the
code which is supported to handle an atomic context. All allocators
have been updated to use KM_SLEEP and the might_sleep() debug macro
has been added to immediately detect atomic callers.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add the ability to dispatch a delayed task to a taskq. The desired
behavior is for the task to be queued but not executed by a worker
thread until the expiration time is reached. To achieve this two
new functions were added.
* taskq_dispatch_delay() -
This function behaves exactly like taskq_dispatch() however it
takes a third 'expire_time' argument. The caller should pass the
desired time the task should be executed as an absolute value in
jiffies. The task is guarenteed not to run before this time, it
may run slightly latter if all the worker threads are busy.
* taskq_cancel_id() -
Given a task id attempt to cancel the task before it gets executed.
This is primarily useful for canceling delay tasks but can be used for
canceling any previously dispatched task. There are three possible
return values.
0 - The task was found and canceled before it was executed.
ENOENT - The task was not found, either it was already run or an
invalid task id was supplied by the caller.
EBUSY - The task is currently executing any may not be canceled.
This function will block until the task has been completed.
* taskq_wait_all() -
The taskq_wait_id() function was renamed taskq_wait_all() to more
clearly reflect its actual behavior. It is only curreny used by
the splat taskq regression tests.
* taskq_wait_id() -
Historically, the only difference between this function and
taskq_wait() was that you passed the task id. In both functions you
would block until ALL lower task ids which executed. This was
semantically correct but could be very slow particularly if there
were delay tasks submitted.
To better accomidate the delay tasks this function was reimplemnted.
It will now only block until the passed task id has been completed.
This is actually a fairly low risk change for a few reasons.
* Only new ZFS callers will make use of the new interfaces and
very little common code was changed to support the new functions.
* The existing taskq_wait() implementation was not changed just
slightly refactored.
* The newly optimized taskq_wait_id() implementation was never
used by ZFS we can't accidentally introduce a new bug there.
NOTE: This functionality does not exist in the Illumos taskqs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When the taskq implementation was originally written I wrapped all
the API functions in #define's. This was done as a preventative
measure to ensure that a taskq symbol never conflicted with an
existing kernel symbol.
However, in practice the taskq symbols never conflicted. The only
major conflicts occured with the kmem cache API. Since this added
layer of obfuscation never bought us anything for the taskq's I'm
removing it.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Update the taskq implementation to conform with the style used
throughout the rest of the code. There are no functional
changes in this commit.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When the Linux 3.6 KERN_PATH_LOCKED compatibility code was added
by commit bcb1589 an entirely new vn_remove() implementation was
added. That function did not properly handle an error from
spl_kern_path_locked() which would result in an panic. This
patch addresses the issue by returning the error to the caller.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#187
Allowing the spl_cache_grow_work() function to reclaim inodes
allows for two unlikely deadlocks. Therefore, we clear __GFP_FS
for these allocations. The two deadlocks are:
* While holding the ZFS_OBJ_HOLD_ENTER(zsb, obj1) lock a function
calls kmem_cache_alloc() which happens to need to allocate a
new slab. To allocate the new slab we enter FS level reclaim
and attempt to evict several inodes. To evict these inodes we
need to take the ZFS_OBJ_HOLD_ENTER(zsb, obj2) lock and it
just happens that obj1 and obj2 use the same hashed lock.
* Similar to the first case however instead of getting blocked
on the hash lock we block in txg_wait_open() which is waiting
for the next txg which isn't coming because the txg_sync
thread is blocked in kmem_cache_alloc().
Note this isn't a 100% fix because vmalloc() won't strictly
honor __GFP_FS. However, it practice this is sufficient because
several very unlikely things must all occur concurrently.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#1101
If we are reaping from the cache and a concurrent allocation
occurs then the caller must block until the reaping is complete.
This is signaled by the clearing of the KMC_BIT_REAPING bit.
Otherwise the caller will be in a tight loop which takes and
releases the skc->skc_cache lock. When there are multiple
concurrent callers the system will thrash on the lock and
appear to lock up.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Because only virtual slabs may have emergency objects and these
objects are guaranteed to have physical addresses. It can be
easily determined if the passed object is a virtual slab object
or an emergency object. This allows us to completely optimize
the emergency object free case out of the common free path.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In the initial implementation emergency objects were tracked on a
per-cache list. The assumption was that under normal operation we
would never allocate more than a handful of these objects. So the
cost of walking the list during free was expected to be negligible.
However real world usage has shown that emergency objects tend to
be allocated in batches. A deadlock will be detected and several
thousand emergency objects will be allocated before the original
blocked slab allocation can complete.
Therefore the original list has been replaced by a red black tree
which is sorted by the memory address of each allocated object.
This bounds the worst case insertion and removal time to O(log n)
which minimize contention on the assoicated spin lock.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The entire goal of performing the slab allocations asynchronously
is to be able to detect when a vmalloc() deadlocks. In this case,
and only this case, do we want to start allocating emergency objects.
The trick here is to minimize false positives because the overhead
of tracking emergency objects is far higher than normal slab objects.
With that goal in mind the code was reworked to be less sensitive
to slow allocations by increasing the wait time. Once a cache is
is marked deadlocked all subsequent allocations which can not be
satisfied with existing cache objects will immediately allocate new
emergency objects. This behavior persists until the asynchronous
allocation completes and clears the deadlocked flag.
The result of these tweaks is that far fewer emergency objects
get created which is important because this minimizes the cost of
releasing them latter in kmem_cache_free().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reference count every entry and exit from the condition variable
functions: cv_wait(), cv_wait_timeout(), cv_signal(), cv_broadcast().
This allows us to safely block in cv_destroy() until all consumers
have been scheduled and are no longer accessing the condition
variable memory.
In addition poison the magic value at the start of cv_destroy() to
ensure there are never any new callers after cv_destroy() is called.
The consumer is responsible for ensuring this never occurs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add a new kstat type for tracking useful statistics about a TXG.
The new KSTAT_TYPE_TXG type can be used to tracks the following
statistics per-txg.
txg - Unique txg number
state - State (O)pen/(Q)uiescing/(S)yncing/(C)ommitted
birth; - Creation time
nread - Bytes read
nwritten; - Bytes written
reads - IOPs read
writes - IOPs write
open_time; - Length in nanoseconds the txg was open
quiesce_time - Length in nanoseconds the txg was quiescing
sync_time; - Length in nanoseconds the txg was syncing
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Move the kstat ks_update() callback under the ks_lock. This
enables dynamically sized kstats without modification to the
kstat API.
* Create a kstat with the KSTAT_FLAG_VIRTUAL flag.
* Register a ->ks_update() callback which does:
o Frees any existing ks_data buffer.
o Set ks_data_size to the kstat array size.
o Set ks_data to an allocated buffer of size ks_data_size
o Populate the array of buffers with the required data.
The buffer allocated in the ks_update() callback is guaranteed
to remain allocated and valid while the proc sequence handler
iterates over the buffer. The lock will not be dropped until
kstat_seq_stop() function is run making it safe for concurrent
access. To allow the ks_update() callback to perform memory
allocations the lock was changed to a mutex.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The kern_path_parent() function was removed from Linux 3.6 because
it was observed that all the callers just want the parent dentry.
The simpler kern_path_locked() function replaces kern_path_parent()
and does the lookup while holding the ->i_mutex lock.
This is good news for the vn implementation because it removes the
need for us to handle the locking. However, it makes it harder to
implement a single readable vn_remove()/vn_rename() function which
is usually what we prefer.
Therefore, we implement a new version of vn_remove()/vn_rename()
for Linux 3.6 and newer kernels. This allows us to leave the
existing working implementation untouched, and to add a simpler
version for newer kernels.
Long term I would very much like to see all of the vn code removed
since what this code enabled is generally frowned upon in the kernel.
But that can't happen util we either abondon the zpool.cache file
or implement alternate infrastructure to update is correctly in
user space.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#154
In this particular instance the allocation occurred in the context
of sys_msync()->...->zpl_putpage() where we must be careful not to
initiate additional I/O.
Signed-off-by: Massimo Maggi <massimo@mmmm.it>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This adds an interface to "punch holes" (deallocate space) in VFS
files. The interface is identical to the Solaris VOP_SPACE interface.
This interface is necessary for TRIM support on file vdevs.
This is implemented using Linux fallocate(FALLOC_FL_PUNCH_HOLE), which
was introduced in 2.6.38. For a brief time before 2.6.38 this was done
using the truncate_range inode operation, which was quickly deprecated.
This patch only supports FALLOC_FL_PUNCH_HOLE.
This adds support for the truncate_range() inode operation to
VOP_SPACE() for file hole punching. This API is deprecated and removed
in 3.5, so it's only useful for old kernels.
On tmpfs, the truncate_range() inode operation translates to
shmem_truncate_range(). Unfortunately, this function expects the end
offset to be inclusive and aligned to the end of a page. If it is not,
the kernel will stop with a BUG_ON().
This patch fixes the issue by adapting to the constraints set forth by
shmem_truncate_range().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#168
Under certain circumstances the following functions may be called
in a context where KM_SLEEP is unsafe and can result in a deadlocked
system. To avoid this problem the unconditional KM_SLEEPs are
converted to KM_PUSHPAGEs. This will prevent them from attempting
to initiate any I/O during direct reclaim.
This change was originally part of cd5ca4b but was reverted by
330fe01. It always should have had its own commit for exactly
this reason.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When the taskq code was originally written it seemed like a good
idea to simply map TQ_SLEEP to KM_SLEEP. Unfortunately, this
assumed that the TQ_* flags would never confict with any of the
Linux GFP_* flags. When adding the TQ_PUSHPAGE support in commit
cd5ca4b this invariant was accidentally broken.
Therefore to support TQ_PUSHPAGE, which is needed for Linux, and
prevent any further confusion I have removed this direct mapping.
The TQ_SLEEP, TQ_NOSLEEP, and TQ_PUSHPAGE are no longer defined
in terms of their KM_* counterparts. Instead a simple mapping
function is introduce to convert TQ_* -> KM_* where needed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #171
This reverts commit cd5ca4b2f8
due to conflicts in the higher TQ_ bits which caused incorrect
behavior.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
There still appears to be a race in the condition variables where
->cv_mutex is set after we are woken from the cv_destroy wait queue.
This might be possible when cv_destroy() is called immediately after
cv_broadcast(). We had some troubles with this previously but
there may still be a small race, see commit d599e4f.
The following patch closes one small race and improves the ASSERTs
such that they log the offending value.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
zfsonlinux/zfs#943
The workspace required by zlib to perform compression is roughly
512MB (order-7). These allocations are so large that we should
never attempt to directly kmalloc an emergency object for them.
It is far preferable to asynchronously vmalloc an additional slab
in case it's needed. Then simply block waiting for an existing
object to be released or for the new slab to be allocated.
This can be accomplished by disabling emergency slab objects by
passing the KMC_NOEMERGENCY flag at slab creation time.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
zfsonlinux/zfs#917
Provide a flag to disable the use of emergency objects for a
specific kmem cache. There may be instances where under no
circumstances should you kmalloc() an emergency object. For
example, when you cache contains very large objects (>128k).
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When various kernel debuging options are enabled this allocation
may be larger than usual as shown by the following warning. It
is in no way harmful so we suppress the warning.
SPL: large kmem_alloc(40960, 0x80d0) at
tsd_hash_table_init:358 (76495/76495)
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#93
Under certain circumstances the following functions may be called
in a context where KM_SLEEP is unsafe and can result in a deadlocked
system. To avoid this problem the unconditional KM_SLEEPs are
converted to KM_PUSHPAGEs. This will prevent them from attempting
to initiate any I/O during direct reclaim.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit 2092cf68d8. The
use of the PF_MEMALLOC flag was always a hack to work around memory
reclaim deadlocks. Those issues are believed to be resolved so this
workaround can be safely reverted.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit b8b6e4c453. The
use of the PF_MEMALLOC flag was always a hack to work around memory
reclaim deadlocks. Those issues are believed to be resolved so this
workaround can be safely reverted.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit 36811b4430.
Which is no longer required because there is now SPL code in
place to safely handle the deadlocks the kernel patch was designed
to address. Therefore we can unconditionally use vmalloc() and
drop all the PF_MEMALLOC code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit 372c257233. The
use of the PF_MEMALLOC flag was always a hack to work around memory
reclaim deadlocks. Those issues are believed to be resolved so this
workaround can be safely reverted.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This patch is designed to resolve a deadlock which can occur with
__vmalloc() based slabs. The issue is that the Linux kernel does
not honor the flags passed to __vmalloc(). This makes it unsafe
to use in a writeback context. Unfortunately, this is a use case
ZFS depends on for correct operation.
Fixing this issue in the upstream kernel was pursued and patches
are available which resolve the issue.
https://bugs.gentoo.org/show_bug.cgi?id=416685
However, these changes were rejected because upstream felt that
using __vmalloc() in the context of writeback should never be done.
Their solution was for us to rewrite parts of ZFS to accomidate
the Linux VM.
While that is probably the right long term solution, and it is
something we want to pursue, it is not a trivial task and will
likely destabilize the existing code. This work has been planned
for the 0.7.0 release but in the meanwhile we want to improve the
SPL slab implementation to accomidate this expected ZFS usage.
This is accomplished by performing the __vmalloc() asynchronously
in the context of a work queue. This doesn't prevent the posibility
of the worker thread from deadlocking. However, the caller can now
safely block on a wait queue for the slab allocation to complete.
Normally this will occur in a reasonable amount of time and the
caller will be woken up when the new slab is available,. The objects
will then get cached in the per-cpu magazines and everything will
proceed as usual.
However, if the __vmalloc() deadlocks for the reasons described
above, or is just very slow, then the callers on the wait queues
will timeout out. When this rare situation occurs they will attempt
to kmalloc() a single minimally sized object using the GFP_NOIO flags.
This allocation will not deadlock because kmalloc() will honor the
passed flags and the caller will be able to make forward progress.
As long as forward progress can be maintained then even if the
worker thread is deadlocked the critical thread will make progress.
This will eventually allow the deadlocked worker thread to complete
and normal operation will resume.
These emergency allocations will likely be slow since they require
contiguous pages. However, their use should be rare so the impact
is expected to be minimal. If that turns out not to be the case in
practice further optimizations are possible.
One additional concern is if these emergency objects are long lived.
Right now they are simply tracked on a list which must be walked when
an object is freed. Is they accumulate on a system and the list
grows freeing objects will become more expensive. This could be
handled relatively easily by using a hash instead of a list, but that
optimization (if needed) is left for a follow up patch.
Additionally, these emeregency objects could be repacked in to existing
slabs as objects are freed if the kmem_cache_set_move() functionality
was implemented. See issue https://github.com/zfsonlinux/spl/issues/26
for full details. This work would also help reduce ZFS's memory
fragmentation problems.
The /proc/spl/kmem/slab file has had two new columns added at the
end. The 'emerg' column reports the current number of these emergency
objects in use for the cache, and the following 'max' column shows
the historical worst case. These value should give us a good idea
of how often these objects are needed. Based on these values under
real use cases we can tune the default behavior.
Lastly, as a side benefit using a single work queue for the slab
allocations should reduce cpu contention on the global virtual address
space lock. This should manifest itself as reduced cpu usage for
the system.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The spl_magazine_age function had the implied assumption that it will
remain on its current cpu through its execution. In order to support
preempt enabled kernels, this assumption had to be removed.
The spl_kmem_magazine structure now holds the cpu id of the cpu it is
local to. This allows spl_magazine_age to use this field when scheduling
work to be done by the magazine's local cpu.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #98
Brian Behlendorf
Turbo Fredriksson
Richard Yao
Ned Bass
Tim Chase
Chunwei Chen
Andrey Vesnovaty
Richard Yao
Tim Chase
Cyril Plisko
Prakash Surya
James H
Yuxuan Shui
Matt Johnston
Massimo Maggi
Etienne Dechamps