This patch achieves the following goals:
1. It replaces the preprocessor kmem flag to gfp flag mapping with
proper translation logic. This eliminates the potential for
surprises that were previously possible where kmem flags were
mapped to gfp flags.
2. It maps vmem_alloc() allocations to kmem_alloc() for allocations
sized less than or equal to the newly-added spl_kmem_alloc_max
parameter. This ensures that small allocations will not contend
on a single global lock, large allocations can still be handled,
and potentially limited virtual address space will not be squandered.
This behavior is entirely different than under Illumos due to
different memory management strategies employed by the respective
kernels. However, this functionally provides the semantics required.
3. The --disable-debug-kmem, --enable-debug-kmem (default), and
--enable-debug-kmem-tracking allocators have been unified in to
a single spl_kmem_alloc_impl() allocation function. This was
done to simplify the code and make it more maintainable.
4. Improve portability by exposing an implementation of the memory
allocations functions that can be safely used in the same way
they are used on Illumos. Specifically, callers may safely
use KM_SLEEP in contexts which perform filesystem IO. This
allows us to eliminate an entire class of Linux specific changes
which were previously required to avoid deadlocking the system.
This change will be largely transparent to existing callers but there
are a few caveats:
1. Because the headers were refactored and extraneous includes removed
callers may find they need to explicitly add additional #includes.
In particular, kmem_cache.h must now be explicitly includes to
access the SPL's kmem cache implementation. This behavior is
different from Illumos but it was done to avoid always masking
the Linux slab functions when kmem.h is included.
2. Callers, like Lustre, which made assumptions about the definitions
of KM_SLEEP, KM_NOSLEEP, and KM_PUSHPAGE will need to be updated.
Other callers such as ZFS which did not will not require changes.
3. KM_PUSHPAGE is no longer overloaded to imply GFP_NOIO. It retains
its original meaning of allowing allocations to access reserved
memory. KM_PUSHPAGE callers can be converted back to KM_SLEEP.
4. The KM_NODEBUG flags has been retired and the default warning
threshold increased to 32k.
5. The kmem_virt() functions has been removed. For callers which
need to distinguish between a physical and virtual address use
is_vmalloc_addr().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change introduces no functional changes to the memory management
interfaces. It only restructures the existing codes by separating the
kmem, vmem, and kmem cache implementations in the separate source and
header files.
Splitting this functionality in to separate files required the addition
of spl_vmem_{init,fini}() and spl_kmem_cache_{initi,fini}() functions.
Additionally, several minor changes to the #include's were required to
accommodate the removal of extraneous header from kmem.h.
But again, while large this patch introduces no functional changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When the SPL was originally written Linux tracepoints were still
in their infancy. Therefore, an entire debugging subsystem was
added to facilite tracing which served us well for many years.
Now that Linux tracepoints have matured they provide all the
functionality of the previous tracing subsystem. Rather than
maintain parallel functionality it makes sense to fully adopt
tracepoints. Therefore, this patch retires the legacy debugging
infrastructure.
See zfsonlinux/zfs@bc9f413 for the tracepoint changes.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#408
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>
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>
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
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>
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
This is a bit of cleanup I'd been meaning to get to for a while
to reduce the chance of a type conflict. Well that conflict
finally occurred with the kstat_init() function which conflicts
with a function in the 2.6.32-6-pve kernel.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#56
Thread specific data has implemented using a hash table, this avoids
the need to add a member to the task structure and allows maximum
portability between kernels. This implementation has been optimized
to keep the tsd_set() and tsd_get() times as small as possible.
The majority of the entries in the hash table are for specific tsd
entries. These entries are hashed by the product of their key and
pid because by design the key and pid are guaranteed to be unique.
Their product also has the desirable properly that it will be uniformly
distributed over the hash bins providing neither the pid nor key is zero.
Under linux the zero pid is always the init process and thus won't be
used, and this implementation is careful to never to assign a zero key.
By default the hash table is sized to 512 bins which is expected to
be sufficient for light to moderate usage of thread specific data.
The hash table contains two additional type of entries. They first
type is entry is called a 'key' entry and it is added to the hash during
tsd_create(). It is used to store the address of the destructor function
and it is used as an anchor point. All tsd entries which use the same
key will be linked to this entry. This is used during tsd_destory() to
quickly call the destructor function for all tsd associated with the key.
The 'key' entry may be looked up with tsd_hash_search() by passing the
key you wish to lookup and DTOR_PID constant as the pid.
The second type of entry is called a 'pid' entry and it is added to the
hash the first time a process set a key. The 'pid' entry is also used
as an anchor and all tsd for the process will be linked to it. This
list is using during tsd_exit() to ensure all registered destructors
are run for the process. The 'pid' entry may be looked up with
tsd_hash_search() by passing the PID_KEY constant as the key, and
the process pid. Note that tsd_exit() is called by thread_exit()
so if your using the Solaris thread API you should not need to call
tsd_exit() directly.
Brian Behlendorf
Richard Yao
Ned Bass
Massimo Maggi