zram writeback is a costly operation, because every target slot (unless
ZRAM_HUGE) is decompressed before it gets written to a backing device.
The writeback to a backing device uses submit_bio_wait() which may look
like a rescheduling point. However, if the backing device has
BD_HAS_SUBMIT_BIO bit set __submit_bio() calls directly
disk->fops->submit_bio(bio) on the backing device and so when
submit_bio_wait() calls blk_wait_io() the I/O is already done. On such
systems we effective end up in a loop
for_each (target slot) {
decompress(slot)
__submit_bio()
disk->fops->submit_bio(bio)
}
Which on PREEMPT_NONE systems triggers watchdogs (since there are no
explicit rescheduling points). Add cond_resched() to the zram writeback
loop.
Link: https://lkml.kernel.org/r/20241218063513.297475-8-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We only can read pages from zspool in writeback, zram_read_page() is not
really right in that context not only because it's a more generic function
that handles ZRAM_WB pages, but also because it requires us to unlock slot
between slot flag check and actual page read. Use zram_read_from_zspool()
instead and do slot flags check and page read under the same slot lock.
Link: https://lkml.kernel.org/r/20241218063513.297475-7-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
zram_write_page() handles: ZRAM_SAME pages (which was already factored
out) stores, regular page stores and ZRAM_HUGE pages stores.
ZRAM_HUGE handling adds a significant amount of complexity. Instead, we
can handle ZRAM_HUGE in a separate function. This allows us to simplify
zs_handle allocations slow-path, as it now does not handle ZRAM_HUGE case.
ZRAM_HUGE zs_handle allocation, on the other hand, can now drop
__GFP_KSWAPD_RECLAIM because we handle ZRAM_HUGE in preemptible context
(outside of local-lock scope).
Link: https://lkml.kernel.org/r/20241218063513.297475-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Handling of ZRAM_SAME now uses a goto to the final stages of
zram_write_page() plus it introduces a branch and flags variable, which is
not making the code any simpler. In reality, we can handle ZRAM_SAME
immediately when we detect such pages and remove a goto and a branch.
Factor out ZRAM_SAME handling into a separate routine to simplify
zram_write_page().
Link: https://lkml.kernel.org/r/20241218063513.297475-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: split page type read/write handling", v2.
This is a subset of [1] series which contains only fixes and improvements
(no new features, as ZRAM_HUGE split is still under consideration).
The motivation for factoring out is that zram_write_page() gets more and
more complex all the time, because it tries to handle too many scenarios:
ZRAM_SAME store, ZRAM_HUGE store, compress page store with zs_malloc
allocation slowpath and conditional recompression, etc. Factor those out
and make things easier to handle.
Addition of cond_resched() is simply a fix, I can trigger watchdog from
zram writeback(). And early slot free is just a reasonable thing to do.
[1] https://lore.kernel.org/linux-kernel/20241119072057.3440039-1-senozhatsky@chromium.org
This patch (of 7):
In the current implementation entry's previously allocated memory is
released in the very last moment, when we already have allocated a new
memory for new data. This, basically, temporarily increases memory usage
for no good reason. For example, consider the case when both old (stale)
and new entry data are incompressible so such entry will temporarily use
two physical pages - one for stale (old) data and one for new data. We
can release old memory as soon as we get a write request for entry.
Link: https://lkml.kernel.org/r/20241218063513.297475-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20241218063513.297475-2-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: fix backing device setup issue", v2.
This series fixes two bugs of backing device setting:
- ZRAM should reject using a zero sized (or the uninitialized ZRAM
device itself) as the backing device.
- Fix backing device leaking when removing a uninitialized ZRAM
device.
This patch (of 2):
Setting a zero sized block device as backing device is pointless, and one
can easily create a recursive loop by setting the uninitialized ZRAM
device itself as its own backing device by (zram0 is uninitialized):
echo /dev/zram0 > /sys/block/zram0/backing_dev
It's definitely a wrong config, and the module will pin itself, kernel
should refuse doing so in the first place.
By refusing to use zero sized device we avoided misuse cases including
this one above.
Link: https://lkml.kernel.org/r/20241209165717.94215-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20241209165717.94215-2-ryncsn@gmail.com
Fixes: 013bf95a83 ("zram: add interface to specif backing device")
Signed-off-by: Kairui Song <kasong@tencent.com>
Reported-by: Desheng Wu <deshengwu@tencent.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: IDLE flag handling fixes", v2.
zram can wrongly preserve ZRAM_IDLE flag on its entries which can result
in premature post-processing (writeback and recompression) of such
entries.
This patch (of 2)
Recompression should clear ZRAM_IDLE flag on the entries it has accessed,
because otherwise some entries, specifically those for which recompression
has failed, become immediate candidate entries for another post-processing
(e.g. writeback).
Consider the following case:
- recompression marks entries IDLE every 4 hours and attempts
to recompress them
- some entries are incompressible, so we keep them intact and
hence preserve IDLE flag
- writeback marks entries IDLE every 8 hours and writebacks
IDLE entries, however we have IDLE entries left from
recompression, so writeback prematurely writebacks those
entries.
The bug was reported by Shin Kawamura.
Link: https://lkml.kernel.org/r/20241028153629.1479791-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20241028153629.1479791-2-senozhatsky@chromium.org
Fixes: 84b33bf788 ("zram: introduce recompress sysfs knob")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Shin Kawamura <kawasin@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Writeback suffers from the same problem as recompression did before -
target slot selection for writeback is just a simple iteration over
zram->table entries (stored pages) which selects suboptimal targets for
writeback. This is especially problematic for writeback, because we
uncompress objects before writeback so each of them takes 4K out of
limited writeback storage. For example, when we take a 48 bytes slot and
store it as a 4K object to writeback device we only save 48 bytes of
memory (release from zsmalloc pool). We naturally want to pick the
largest objects for writeback, because then each writeback will release
the largest amount of memory.
This patch applies the same solution and strategy as for recompression
target selection: pp control (post-process) with 16 buckets of candidate
pp slots. Slots are assigned to pp buckets based on sizes - the larger
the slot the higher the group index. This gives us sorted by size lists
of candidate slots (in linear time), so that among post-processing
candidate slots we always select the largest ones first and maximize the
memory saving.
TEST
====
A very simple demonstration: zram is configured with a writeback device.
A limited writeback (wb_limit 2500 pages) is performed then, with a log of
sizes of slots that were written back. You can see that patched zram
selects slots for recompression in significantly different manner, which
leads to higher memory savings (see column #2 of mm_stat output).
BASE
----
*** initial state of zram device
/sys/block/zram0/mm_stat
1750327296 619765836 631902208 0 631902208 1 0 34278 34278
*** writeback idle wb_limit 2500
/sys/block/zram0/mm_stat
1750327296 617622333 631578624 0 631902208 1 0 34278 34278
Sizes of selected objects for writeback:
... 193 349 46 46 46 46 852 1002 543 162 107 49 34 34 34 ...
PATCHED
-------
*** initial state of zram device
/sys/block/zram0/mm_stat
1750319104 619760957 631992320 0 631992320 1 0 34278 34278
*** writeback idle wb_limit 2500
/sys/block/zram0/mm_stat
1750319104 612672056 626135040 0 631992320 1 0 34278 34278
Sizes of selected objects for writeback:
... 3667 3580 3581 3580 3581 3581 3581 3231 3211 3203 3231 3246 ...
Note, pp-slots are not strictly sorted, there is a PP_BUCKET_SIZE_RANGE
variation of sizes within particular bucket.
Link: https://lkml.kernel.org/r/20240917021020.883356-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Target slot selection for recompression is just a simple iteration over
zram->table entries (stored pages) from slot 0 to max slot. Given that
zram->table slots are written in random order and are not sorted by size,
a simple iteration over slots selects suboptimal targets for
recompression. This is not a problem if we recompress every single
zram->table slot, but we never do that in reality. In reality we limit
the number of slots we can recompress (via max_pages parameter) and hence
proper slot selection becomes very important. The strategy is quite
simple, suppose we have two candidate slots for recompression, one of size
48 bytes and one of size 2800 bytes, and we can recompress only one, then
it certainly makes more sense to pick 2800 entry for recompression.
Because even if we manage to compress 48 bytes objects even further the
savings are going to be very small. Potential savings after good
re-compression of 2800 bytes objects are much higher.
This patch reworks slot selection and introduces the strategy described
above: among candidate slots always select the biggest ones first.
For that the patch introduces zram_pp_ctl (post-processing) structure
which holds NUM_PP_BUCKETS pp buckets of slots. Slots are assigned to a
particular group based on their sizes - the larger the size of the slot
the higher the group index. This, basically, sorts slots by size in liner
time (we still perform just one iteration over zram->table slots). When
we select slot for recompression we always first lookup in higher pp
buckets (those that hold the largest slots). Which achieves the desired
behavior.
TEST
====
A very simple demonstration: zram is configured with zstd, and zstd with
dict as a recompression stream. A limited (max 4096 pages) recompression
is performed then, with a log of sizes of slots that were recompressed.
You can see that patched zram selects slots for recompression in
significantly different manner, which leads to higher memory savings (see
column #2 of mm_stat output).
BASE
----
*** initial state of zram device
/sys/block/zram0/mm_stat
1750994944 504491413 514203648 0 514203648 1 0 34204 34204
*** recompress idle max_pages=4096
/sys/block/zram0/mm_stat
1750994944 504262229 514953216 0 514203648 1 0 34204 34204
Sizes of selected objects for recompression:
... 45 58 24 226 91 40 24 24 24 424 2104 93 2078 2078 2078 959 154 ...
PATCHED
-------
*** initial state of zram device
/sys/block/zram0/mm_stat
1750982656 504492801 514170880 0 514170880 1 0 34204 34204
*** recompress idle max_pages=4096
/sys/block/zram0/mm_stat
1750982656 503716710 517586944 0 514170880 1 0 34204 34204
Sizes of selected objects for recompression:
... 3680 3694 3667 3590 3614 3553 3537 3548 3550 3542 3543 3537 ...
Note, pp-slots are not strictly sorted, there is a PP_BUCKET_SIZE_RANGE
variation of sizes within particular bucket.
[senozhatsky@chromium.org: do not skip the first bucket]
Link: https://lkml.kernel.org/r/20241001085634.1948384-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20240917021020.883356-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Both recompress and writeback soon will unlock slots during processing,
which makes things too complex wrt possible race-conditions. We still
want to clear PP_SLOT in slot_free, because this is how we figure out that
slot that was selected for post-processing has been released under us and
when we start post-processing we check if slot still has PP_SLOT set. At
the same time, theoretically, we can have something like this:
CPU0 CPU1
recompress
scan slots
set PP_SLOT
unlock slot
slot_free
clear PP_SLOT
allocate PP_SLOT
writeback
scan slots
set PP_SLOT
unlock slot
select PP-slot
test PP_SLOT
So recompress will not detect that slot has been re-used and re-selected
for concurrent writeback post-processing.
Make sure that we only permit on post-processing operation at a time. So
now recompress and writeback post-processing don't race against each
other, we only need to handle slot re-use (slot_free and write), which is
handled individually by each pp operation.
Having recompress and writeback competing for the same slots is not
exactly good anyway (can't imagine anyone doing that).
Link: https://lkml.kernel.org/r/20240917021020.883356-3-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: optimal post-processing target selection", v5.
Problem:
--------
Both recompression and writeback perform a very simple linear scan of all
zram slots in search for post-processing (writeback or recompress)
candidate slots. This often means that we pick the worst candidate for pp
(post-processing), e.g. a 48 bytes object for writeback, which is nearly
useless, because it only releases 48 bytes from zsmalloc pool, but
consumes an entire 4K slot in the backing device. Similarly,
recompression of an 48 bytes objects is unlikely to save more memory that
recompression of a 3000 bytes object. Both recompression and writeback
consume constrained resources (CPU time, batter, backing device storage
space) and quite often have a (daily) limit on the number of items they
post-process, so we should utilize those constrained resources in the most
optimal way.
Solution:
---------
This patch reworks the way we select pp targets. We, quite clearly, want
to sort all the candidates and always pick the largest, be it
recompression or writeback. Especially for writeback, because the larger
object we writeback the more memory we release. This series introduces
concept of pp buckets and pp scan/selection.
The scan step is a simple iteration over all zram->table entries, just
like what we currently do, but we don't post-process a candidate slot
immediately. Instead we assign it to a PP (post-processing) bucket. PP
bucket is, basically, a list which holds pp candidate slots that belong to
the same size class. PP buckets are 64 bytes apart, slots are not
strictly sorted within a bucket there is a 64 bytes variance.
The select step simply iterates over pp buckets from highest to lowest and
picks all candidate slots a particular buckets contains. So this gives us
sorted candidates (in linear time) and allows us to select most optimal
(largest) candidates for post-processing first.
This patch (of 7):
This flag indicates that the slot was selected as a candidate slot for
post-processing (pp) and was assigned to a pp bucket. It does not
necessarily mean that the slot is currently under post-processing, but may
mean so. The slot can loose its PP_SLOT flag, while still being in the
pp-bucket, if it's accessed or slot_free-ed.
Link: https://lkml.kernel.org/r/20240917021020.883356-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20240917021020.883356-2-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull MM updates from Andrew Morton:
"Along with the usual shower of singleton patches, notable patch series
in this pull request are:
- "Align kvrealloc() with krealloc()" from Danilo Krummrich. Adds
consistency to the APIs and behaviour of these two core allocation
functions. This also simplifies/enables Rustification.
- "Some cleanups for shmem" from Baolin Wang. No functional changes -
mode code reuse, better function naming, logic simplifications.
- "mm: some small page fault cleanups" from Josef Bacik. No
functional changes - code cleanups only.
- "Various memory tiering fixes" from Zi Yan. A small fix and a
little cleanup.
- "mm/swap: remove boilerplate" from Yu Zhao. Code cleanups and
simplifications and .text shrinkage.
- "Kernel stack usage histogram" from Pasha Tatashin and Shakeel
Butt. This is a feature, it adds new feilds to /proc/vmstat such as
$ grep kstack /proc/vmstat
kstack_1k 3
kstack_2k 188
kstack_4k 11391
kstack_8k 243
kstack_16k 0
which tells us that 11391 processes used 4k of stack while none at
all used 16k. Useful for some system tuning things, but
partivularly useful for "the dynamic kernel stack project".
- "kmemleak: support for percpu memory leak detect" from Pavel
Tikhomirov. Teaches kmemleak to detect leaksage of percpu memory.
- "mm: memcg: page counters optimizations" from Roman Gushchin. "3
independent small optimizations of page counters".
- "mm: split PTE/PMD PT table Kconfig cleanups+clarifications" from
David Hildenbrand. Improves PTE/PMD splitlock detection, makes
powerpc/8xx work correctly by design rather than by accident.
- "mm: remove arch_make_page_accessible()" from David Hildenbrand.
Some folio conversions which make arch_make_page_accessible()
unneeded.
- "mm, memcg: cg2 memory{.swap,}.peak write handlers" fro David
Finkel. Cleans up and fixes our handling of the resetting of the
cgroup/process peak-memory-use detector.
- "Make core VMA operations internal and testable" from Lorenzo
Stoakes. Rationalizaion and encapsulation of the VMA manipulation
APIs. With a view to better enable testing of the VMA functions,
even from a userspace-only harness.
- "mm: zswap: fixes for global shrinker" from Takero Funaki. Fix
issues in the zswap global shrinker, resulting in improved
performance.
- "mm: print the promo watermark in zoneinfo" from Kaiyang Zhao. Fill
in some missing info in /proc/zoneinfo.
- "mm: replace follow_page() by folio_walk" from David Hildenbrand.
Code cleanups and rationalizations (conversion to folio_walk())
resulting in the removal of follow_page().
- "improving dynamic zswap shrinker protection scheme" from Nhat
Pham. Some tuning to improve zswap's dynamic shrinker. Significant
reductions in swapin and improvements in performance are shown.
- "mm: Fix several issues with unaccepted memory" from Kirill
Shutemov. Improvements to the new unaccepted memory feature,
- "mm/mprotect: Fix dax puds" from Peter Xu. Implements mprotect on
DAX PUDs. This was missing, although nobody seems to have notied
yet.
- "Introduce a store type enum for the Maple tree" from Sidhartha
Kumar. Cleanups and modest performance improvements for the maple
tree library code.
- "memcg: further decouple v1 code from v2" from Shakeel Butt. Move
more cgroup v1 remnants away from the v2 memcg code.
- "memcg: initiate deprecation of v1 features" from Shakeel Butt.
Adds various warnings telling users that memcg v1 features are
deprecated.
- "mm: swap: mTHP swap allocator base on swap cluster order" from
Chris Li. Greatly improves the success rate of the mTHP swap
allocation.
- "mm: introduce numa_memblks" from Mike Rapoport. Moves various
disparate per-arch implementations of numa_memblk code into generic
code.
- "mm: batch free swaps for zap_pte_range()" from Barry Song. Greatly
improves the performance of munmap() of swap-filled ptes.
- "support large folio swap-out and swap-in for shmem" from Baolin
Wang. With this series we no longer split shmem large folios into
simgle-page folios when swapping out shmem.
- "mm/hugetlb: alloc/free gigantic folios" from Yu Zhao. Nice
performance improvements and code reductions for gigantic folios.
- "support shmem mTHP collapse" from Baolin Wang. Adds support for
khugepaged's collapsing of shmem mTHP folios.
- "mm: Optimize mseal checks" from Pedro Falcato. Fixes an mprotect()
performance regression due to the addition of mseal().
- "Increase the number of bits available in page_type" from Matthew
Wilcox. Increases the number of bits available in page_type!
- "Simplify the page flags a little" from Matthew Wilcox. Many legacy
page flags are now folio flags, so the page-based flags and their
accessors/mutators can be removed.
- "mm: store zero pages to be swapped out in a bitmap" from Usama
Arif. An optimization which permits us to avoid writing/reading
zero-filled zswap pages to backing store.
- "Avoid MAP_FIXED gap exposure" from Liam Howlett. Fixes a race
window which occurs when a MAP_FIXED operqtion is occurring during
an unrelated vma tree walk.
- "mm: remove vma_merge()" from Lorenzo Stoakes. Major rotorooting of
the vma_merge() functionality, making ot cleaner, more testable and
better tested.
- "misc fixups for DAMON {self,kunit} tests" from SeongJae Park.
Minor fixups of DAMON selftests and kunit tests.
- "mm: memory_hotplug: improve do_migrate_range()" from Kefeng Wang.
Code cleanups and folio conversions.
- "Shmem mTHP controls and stats improvements" from Ryan Roberts.
Cleanups for shmem controls and stats.
- "mm: count the number of anonymous THPs per size" from Barry Song.
Expose additional anon THP stats to userspace for improved tuning.
- "mm: finish isolate/putback_lru_page()" from Kefeng Wang: more
folio conversions and removal of now-unused page-based APIs.
- "replace per-quota region priorities histogram buffer with
per-context one" from SeongJae Park. DAMON histogram
rationalization.
- "Docs/damon: update GitHub repo URLs and maintainer-profile" from
SeongJae Park. DAMON documentation updates.
- "mm/vdpa: correct misuse of non-direct-reclaim __GFP_NOFAIL and
improve related doc and warn" from Jason Wang: fixes usage of page
allocator __GFP_NOFAIL and GFP_ATOMIC flags.
- "mm: split underused THPs" from Yu Zhao. Improve THP=always policy.
This was overprovisioning THPs in sparsely accessed memory areas.
- "zram: introduce custom comp backends API" frm Sergey Senozhatsky.
Add support for zram run-time compression algorithm tuning.
- "mm: Care about shadow stack guard gap when getting an unmapped
area" from Mark Brown. Fix up the various arch_get_unmapped_area()
implementations to better respect guard areas.
- "Improve mem_cgroup_iter()" from Kinsey Ho. Improve the reliability
of mem_cgroup_iter() and various code cleanups.
- "mm: Support huge pfnmaps" from Peter Xu. Extends the usage of huge
pfnmap support.
- "resource: Fix region_intersects() vs add_memory_driver_managed()"
from Huang Ying. Fix a bug in region_intersects() for systems with
CXL memory.
- "mm: hwpoison: two more poison recovery" from Kefeng Wang. Teaches
a couple more code paths to correctly recover from the encountering
of poisoned memry.
- "mm: enable large folios swap-in support" from Barry Song. Support
the swapin of mTHP memory into appropriately-sized folios, rather
than into single-page folios"
* tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (416 commits)
zram: free secondary algorithms names
uprobes: turn xol_area->pages[2] into xol_area->page
uprobes: introduce the global struct vm_special_mapping xol_mapping
Revert "uprobes: use vm_special_mapping close() functionality"
mm: support large folios swap-in for sync io devices
mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios
mm: fix swap_read_folio_zeromap() for large folios with partial zeromap
mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries
set_memory: add __must_check to generic stubs
mm/vma: return the exact errno in vms_gather_munmap_vmas()
memcg: cleanup with !CONFIG_MEMCG_V1
mm/show_mem.c: report alloc tags in human readable units
mm: support poison recovery from copy_present_page()
mm: support poison recovery from do_cow_fault()
resource, kunit: add test case for region_intersects()
resource: make alloc_free_mem_region() works for iomem_resource
mm: z3fold: deprecate CONFIG_Z3FOLD
vfio/pci: implement huge_fault support
mm/arm64: support large pfn mappings
mm/x86: support large pfn mappings
...
recompress device attribute supports alg=NAME parameter so that we can
specify only one particular algorithm we want to perform recompression
with. However, with algo params we now can have several exactly same
secondary algorithms but each with its own params tuning (e.g. priority 1
configured to use more aggressive level, and priority 2 configured to use
a pre-trained dictionary). Support priority=NUM parameter so that we can
correctly determine which secondary algorithm we want to use.
Link: https://lkml.kernel.org/r/20240902105656.1383858-25-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Support pre-trained dictionary param. lz4 doesn't mandate specific format
of the dictionary and even zstd --train can be used to train a dictionary
for lz4, according to [1].
TEST
====
*** lz4
/sys/block/zram0/mm_stat
1750654976 664188565 676864000 0 676864000 1 0 34288 34288
*** lz4 dict=/etc/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750638592 619891141 632053760 0 632053760 1 0 34278 34278
*** lz4 level=5 dict=/etc/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750638592 727174243 740810752 0 740810752 1 0 34437 34437
[1] https://github.com/lz4/lz4/issues/557
Link: https://lkml.kernel.org/r/20240902105656.1383858-21-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Immutable params never change once comp has been allocated and setup, so
we don't need to store multiple copies of them in each per-CPU backend
context. Move those to per-comp zcomp_params and pass it to backends
callbacks for requests execution. Basically, this means parameters
sharing between different contexts.
Also introduce two new backends callbacks: setup_params() and
release_params(). First, we need to validate params in a driver-specific
way; second, driver may want to allocate its specific representation of
the params which is needed to execute requests.
Link: https://lkml.kernel.org/r/20240902105656.1383858-20-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This attribute is used to setup compression algorithms' parameters, so we
can tweak algorithms' characteristics. At this point only 'level' is
supported (to be extended in the future).
Each call sets up parameters for one particular algorithm, which should be
specified either by the algorithm's priority or algo name. This is
expected to be called after corresponding algorithm is selected via
comp_algorithm or recomp_algorithm.
echo "priority=0 level=1" > /sys/block/zram0/algorithm_params
or
echo "algo=zstd level=1" > /sys/block/zram0/algorithm_params
Link: https://lkml.kernel.org/r/20240902105656.1383858-16-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The zram_table_entry::flags member is of type long and uses 8 bytes on a
64bit architecture. With a PAGE_SIZE of 256KiB we have PAGE_SHIFT of 18
which in turn leads to __NR_ZRAM_PAGEFLAGS = 27. This still fits in an
ordinary integer.
By reducing the size of `flags' to four bytes, the size of the struct
goes back to 16 bytes. The padding between the lock and ac_time (if
enabled) is also gone.
Make zram_table_entry::flags an unsigned int and update the build test
to reflect the change.
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240906141520.730009-4-bigeasy@linutronix.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The bit spinlock disables preemption. The spinlock_t lock becomes a sleeping
lock on PREEMPT_RT and it can not be acquired in this context. In this locked
section, zs_free() acquires a zs_pool::lock, and there is access to
zram::wb_limit_lock.
Add a spinlock_t for locking. Keep the set/ clear ZRAM_LOCK bit after
the lock has been acquired/ dropped. The size of struct zram_table_entry
increases by 4 bytes due to lock and additional 4 bytes padding with
CONFIG_ZRAM_TRACK_ENTRY_ACTIME enabled.
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240906141520.730009-2-bigeasy@linutronix.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
