Currently the ARC state (MFU/MRU) of cached L2ARC buffer and their
content type is unknown. Knowing this information may prove beneficial
in adjusting the L2ARC caching policy.
This commit adds L2ARC arcstats that display the aligned size
(in bytes) of L2ARC buffers according to their content type
(data/metadata) and according to their ARC state (MRU/MFU or
prefetch). It also expands the existing evict_l2_eligible arcstat to
differentiate between MFU and MRU buffers.
L2ARC caches buffers from the MRU and MFU lists of ARC. Upon caching a
buffer, its ARC state (MRU/MFU) is stored in the L2 header
(b_arcs_state). The l2_m{f,r}u_asize arcstats reflect the aligned size
(in bytes) of L2ARC buffers according to their ARC state (based on
b_arcs_state). We also account for the case where an L2ARC and ARC
cached MRU or MRU_ghost buffer transitions to MFU. The l2_prefetch_asize
reflects the alinged size (in bytes) of L2ARC buffers that were cached
while they had the prefetch flag set in ARC. This is dynamically updated
as the prefetch flag of L2ARC buffers changes.
When buffers are evicted from ARC, if they are determined to be L2ARC
eligible then their logical size is recorded in
evict_l2_eligible_m{r,f}u arcstats according to their ARC state upon
eviction.
Persistent L2ARC:
When committing an L2ARC buffer to a log block (L2ARC metadata) its
b_arcs_state and prefetch flag is also stored. If the buffer changes
its arcstate or prefetch flag this is reflected in the above arcstats.
However, the L2ARC metadata cannot currently be updated to reflect this
change.
Example: L2ARC caches an MRU buffer. L2ARC metadata and arcstats count
this as an MRU buffer. The buffer transitions to MFU. The arcstats are
updated to reflect this. Upon pool re-import or on/offlining the L2ARC
device the arcstats are cleared and the buffer will now be counted as an
MRU buffer, as the L2ARC metadata were not updated.
Bug fix:
- If l2arc_noprefetch is set, arc_read_done clears the L2CACHE flag of
an ARC buffer. However, prefetches may be issued in a way that
arc_read_done() is bypassed. Instead, move the related code in
l2arc_write_eligible() to account for those cases too.
Also add a test and update manpages for l2arc_mfuonly module parameter,
and update the manpages and code comments for l2arc_noprefetch.
Move persist_l2arc tests to l2arc.
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes#10743
* Use all caps for document title.
* Remove section name as it can be inferred from the section number.
* Name "OpenZFS" as the document source.
* Bump modification date.
While here, fixed trailing whitespace reported by igor.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#10792
The meaning of the `free` field is currently `zfs_arc_sys_free`, which
is the target amount of memory to leave free for the system, and is
constant after booting.
This commit changes the meaning of `free` to arc_free_memory(), the
amount of memory that the ARC considers to be free.
It also adds a new arcstat field `avail`, which tracks
`arc_available_memory()`.
Since `avail` can be negative, it also updates the arcstat script to
pretty-print negative values.
example output:
$ arcstat -f time,miss,arcsz,c,grow,need,free,avail 1
time miss arcsz c grow need free avail
15:03:02 39K 114G 114G 0 0 2.4G 407M
15:03:03 42K 114G 114G 0 0 2.1G 120M
15:03:04 40K 114G 114G 0 0 1.8G -177M
15:03:05 24K 113G 112G 0 0 1.7G -269M
15:03:06 29K 111G 110G 0 0 1.6G -385M
15:03:07 27K 110G 108G 0 0 1.4G -535M
15:03:08 13K 108G 108G 0 0 2.2G 239M
15:03:09 33K 107G 107G 0 0 1.3G -639M
15:03:10 16K 105G 102G 0 0 2.6G 704M
15:03:11 7.2K 102G 102G 0 0 5.1G 3.1G
15:03:12 42K 103G 102G 0 0 4.8G 2.8G
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes#10494
Turns out the illumos manpage, which is what this originates from, was
written for the original Perl version of the utility which is not the
version in the OpenZFS tree. *That* version originates from a Python
rewrite that was done for FreeNAS. So fix up the manpage to match what
we actually ship (and fix a few typos in the process).
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: AJ Jordan <alex@strugee.net>
Closes#10288
And move it from section 1m to section 1 for consistency.
Imported from illumos commit f34d737f.
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: AJ Jordan <alex@strugee.net>
Closes#10288
George Amanakis
Ryan Moeller
Matthew Ahrens
AJ Jordan