18 Mar, 2016
2 commits
-
Add a new column to pool stats, which will tell how many pages ideally
can be freed by class compaction, so it will be easier to analyze
zsmalloc fragmentation.At the moment, we have only numbers of FULL and ALMOST_EMPTY classes,
but they don't tell us how badly the class is fragmented internally.The new /sys/kernel/debug/zsmalloc/zramX/classes output look as follows:
class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable
[..]
12 224 0 2 146 5 8 4 4
13 240 0 0 0 0 0 1 0
14 256 1 13 1840 1672 115 1 10
15 272 0 0 0 0 0 1 0
[..]
49 816 0 3 745 735 149 1 2
51 848 3 4 361 306 76 4 8
52 864 12 14 378 268 81 3 21
54 896 1 12 117 57 26 2 12
57 944 0 0 0 0 0 3 0
[..]
Total 26 131 12709 10994 1071 134For example, from this particular output we can easily conclude that
class-896 is heavily fragmented -- it occupies 26 pages, 12 can be freed
by compaction.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When unmapping a huge class page in zs_unmap_object, the page will be
unmapped by kmap_atomic. the "!area->huge" branch in __zs_unmap_object
is alway true, and no code set "area->huge" now, so we can drop it.Signed-off-by: YiPing Xu
Reviewed-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Jan, 2016
1 commit
-
record_obj() in migrate_zspage() does not preserve handle's
HANDLE_PIN_BIT, set by find_aloced_obj()->trypin_tag(), and implicitly
(accidentally) un-pins the handle, while migrate_zspage() still performs
an explicit unpin_tag() on the that handle. This additional explicit
unpin_tag() introduces a race condition with zs_free(), which can pin
that handle by this time, so the handle becomes un-pinned.Schematically, it goes like this:
CPU0 CPU1
migrate_zspage
find_alloced_obj
trypin_tag
set HANDLE_PIN_BIT zs_free()
pin_tag()
obj_malloc() -- new object, no tag
record_obj() -- remove HANDLE_PIN_BIT set HANDLE_PIN_BIT
unpin_tag() -- remove zs_free's HANDLE_PIN_BITThe race condition may result in a NULL pointer dereference:
Unable to handle kernel NULL pointer dereference at virtual address 00000000
CPU: 0 PID: 19001 Comm: CookieMonsterCl Tainted:
PC is at get_zspage_mapping+0x0/0x24
LR is at obj_free.isra.22+0x64/0x128
Call trace:
get_zspage_mapping+0x0/0x24
zs_free+0x88/0x114
zram_free_page+0x64/0xcc
zram_slot_free_notify+0x90/0x108
swap_entry_free+0x278/0x294
free_swap_and_cache+0x38/0x11c
unmap_single_vma+0x480/0x5c8
unmap_vmas+0x44/0x60
exit_mmap+0x50/0x110
mmput+0x58/0xe0
do_exit+0x320/0x8dc
do_group_exit+0x44/0xa8
get_signal+0x538/0x580
do_signal+0x98/0x4b8
do_notify_resume+0x14/0x5cThis patch keeps the lock bit in migration path and update value
atomically.Signed-off-by: Junil Lee
Signed-off-by: Minchan Kim
Acked-by: Vlastimil Babka
Cc: Sergey Senozhatsky
Cc: [4.1+]
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Jan, 2016
1 commit
-
Reoder the pages_per_zspage field in struct size_class which can
eliminate the 4 bytes hole between it and stats field.Signed-off-by: Weijie Yang
Reviewed-by: Sergey Senozhatsky
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Nov, 2015
8 commits
-
We are going to rework how compound_head() work. It will not use
page->first_page as we have it now.The only other user of page->first_page beyond compound pages is
zsmalloc.Let's use page->private instead of page->first_page here. It occupies
the same storage space.Signed-off-by: Kirill A. Shutemov
Acked-by: Vlastimil Babka
Reviewed-by: Sergey Senozhatsky
Reviewed-by: Andrea Arcangeli
Cc: "Paul E. McKenney"
Cc: Andi Kleen
Cc: Aneesh Kumar K.V
Cc: Christoph Lameter
Cc: David Rientjes
Cc: Hugh Dickins
Cc: Joonsoo Kim
Cc: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Each `struct size_class' contains `struct zs_size_stat': an array of
NR_ZS_STAT_TYPE `unsigned long'. For zsmalloc built with no
CONFIG_ZSMALLOC_STAT this results in a waste of `2 * sizeof(unsigned
long)' per-class.The patch removes unneeded `struct zs_size_stat' members by redefining
NR_ZS_STAT_TYPE (max stat idx in array).Since both NR_ZS_STAT_TYPE and zs_stat_type are compile time constants,
GCC can eliminate zs_stat_inc()/zs_stat_dec() calls that use zs_stat_type
larger than NR_ZS_STAT_TYPE: CLASS_ALMOST_EMPTY and CLASS_ALMOST_FULL at
the moment../scripts/bloat-o-meter mm/zsmalloc.o.old mm/zsmalloc.o.new
add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-39 (-39)
function old new delta
fix_fullness_group 97 94 -3
insert_zspage 100 86 -14
remove_zspage 141 119 -22To summarize:
a) each class now uses less memory
b) we avoid a number of dec/inc stats (a minor optimization,
but still).The gain will increase once we introduce additional stats.
A simple IO test.
iozone -t 4 -R -r 32K -s 60M -I +Z
patched base
" Initial write " 4145599.06 4127509.75
" Rewrite " 4146225.94 4223618.50
" Read " 17157606.00 17211329.50
" Re-read " 17380428.00 17267650.50
" Reverse Read " 16742768.00 16162732.75
" Stride read " 16586245.75 16073934.25
" Random read " 16349587.50 15799401.75
" Mixed workload " 10344230.62 9775551.50
" Random write " 4277700.62 4260019.69
" Pwrite " 4302049.12 4313703.88
" Pread " 6164463.16 6126536.72
" Fwrite " 7131195.00 6952586.00
" Fread " 12682602.25 12619207.50Signed-off-by: Sergey Senozhatsky
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Hui Zhu
Reviewed-by: Sergey Senozhatsky
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We don't let user to disable shrinker in zsmalloc (once it's been
enabled), so no need to check ->shrinker_enabled in zs_shrinker_count(),
at the moment at least.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
A cosmetic change.
Commit c60369f01125 ("staging: zsmalloc: prevent mappping in interrupt
context") added in_interrupt() check to zs_map_object() and 'hardirq.h'
include; but in_interrupt() macro is defined in 'preempt.h' not in
'hardirq.h', so include it instead.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In obj_malloc():
if (!class->huge)
/* record handle in the header of allocated chunk */
link->handle = handle;
else
/* record handle in first_page->private */
set_page_private(first_page, handle);In the hugepage we save handle to private directly.
But in obj_to_head():
if (class->huge) {
VM_BUG_ON(!is_first_page(page));
return *(unsigned long *)page_private(page);
} else
return *(unsigned long *)obj;It is used as a pointer.
The reason why there is no problem until now is huge-class page is born
with ZS_FULL so it can't be migrated. However, we need this patch for
future work: "VM-aware zsmalloced page migration" to reduce external
fragmentation.Signed-off-by: Hui Zhu
Acked-by: Minchan Kim
Cc: Sergey Senozhatsky
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
[akpm@linux-foundation.org: fix grammar]
Signed-off-by: Hui Zhu
Reviewed-by: Sergey Senozhatsky
Cc: Dan Streetman
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Constify `struct zs_pool' ->name.
[akpm@inux-foundation.org: constify zpool_create_pool()'s `type' arg also]
Signed-off-by: Sergey Senozhatsky
Acked-by: Dan Streetman
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 Sep, 2015
13 commits
-
The structure zpool_ops is not modified so make the pointer to it a
pointer to const.Signed-off-by: Krzysztof Kozlowski
Acked-by: Dan Streetman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We can pass a NULL cache pointer to kmem_cache_destroy(), because it
NULL-checks its argument now. Remove redundant test from
destroy_handle_cache().Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We can avoid taking class ->lock around zs_can_compact() in
zs_shrinker_count(), because the number that we return back is outdated
in general case, by design. We have different sources that are able to
change class's state right after we return from zs_can_compact() --
ongoing I/O operations, manually triggered compaction, or two of them
happening simultaneously.We re-do this calculations during compaction on a per class basis
anyway.zs_unregister_shrinker() will not return until we have an active
shrinker, so classes won't unexpectedly disappear while
zs_shrinker_count() iterates them.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There is no need to recalcurate pages_per_zspage in runtime. Just use
class->pages_per_zspage to avoid unnecessary runtime overhead.Signed-off-by: Minchan Kim
Acked-by: Sergey Senozhatsky
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There is no reason to prevent select ZS_ALMOST_FULL as migration source
if we cannot find source from ZS_ALMOST_EMPTY.With this patch, zs_can_compact will return more exact result.
Signed-off-by: Minchan Kim
Acked-by: Sergey Senozhatsky
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We want to see more ZS_FULL pages and less ZS_ALMOST_{FULL, EMPTY}
pages. Put a page with higher ->inuse count first within its
->fullness_list, which will give us better chances to fill up this page
with new objects (find_get_zspage() return ->fullness_list head for new
object allocation), so some zspages will become ZS_ALMOST_FULL/ZS_FULL
quicker.It performs a trivial and cheap ->inuse compare which does not slow down
zsmalloc and in the worst case keeps the list pages in no particular
order.A more expensive solution could sort fullness_list by ->inuse count.
[minchan@kernel.org: code adjustments]
Signed-off-by: Sergey Senozhatsky
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Perform automatic pool compaction by a shrinker when system is getting
tight on memory.User-space has a very little knowledge regarding zsmalloc fragmentation
and basically has no mechanism to tell whether compaction will result in
any memory gain. Another issue is that user space is not always aware
of the fact that system is getting tight on memory. Which leads to very
uncomfortable scenarios when user space may start issuing compaction
'randomly' or from crontab (for example). Fragmentation is not always
necessarily bad, allocated and unused objects, after all, may be filled
with the data later, w/o the need of allocating a new zspage. On the
other hand, we obviously don't want to waste memory when the system
needs it.Compaction now has a relatively quick pool scan so we are able to
estimate the number of pages that will be freed easily, which makes it
possible to call this function from a shrinker->count_objects()
callback. We also abort compaction as soon as we detect that we can't
free any pages any more, preventing wasteful objects migrations.Signed-off-by: Sergey Senozhatsky
Suggested-by: Minchan Kim
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Compaction returns back to zram the number of migrated objects, which is
quite uninformative -- we have objects of different sizes so user space
cannot obtain any valuable data from that number. Change compaction to
operate in terms of pages and return back to compaction issuer the
number of pages that were freed during compaction. So from now on we
will export more meaningful value in zram/mm_stat -- the number of
freed (compacted) pages.This requires:
(a) a rename of `num_migrated' to 'pages_compacted'
(b) a internal API change -- return first_page's fullness_group from
putback_zspage(), so we know when putback_zspage() did
free_zspage(). It helps us to account compaction stats correctly.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
`zs_compact_control' accounts the number of migrated objects but it has
a limited lifespan -- we lose it as soon as zs_compaction() returns back
to zram. It worked fine, because (a) zram had it's own counter of
migrated objects and (b) only zram could trigger compaction. However,
this does not work for automatic pool compaction (not issued by zram).
To account objects migrated during auto-compaction (issued by the
shrinker) we need to store this number in zs_pool.Define a new `struct zs_pool_stats' structure to keep zs_pool's stats
there. It provides only `num_migrated', as of this writing, but it
surely can be extended.A new zsmalloc zs_pool_stats() symbol exports zs_pool's stats back to
caller.Use zs_pool_stats() in zram and remove `num_migrated' from zram_stats.
Signed-off-by: Sergey Senozhatsky
Suggested-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Change zs_object_copy() argument order to be (DST, SRC) rather than
(SRC, DST). copy/move functions usually have (to, from) arguments
order.Rename alloc_target_page() to isolate_target_page(). This function
doesn't allocate anything, it isolates target page, pretty much like
isolate_source_page().Tweak __zs_compact() comment.
Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This function checks if class compaction will free any pages.
Rephrasing -- do we have enough unused objects to form at least one
ZS_EMPTY page and free it. It aborts compaction if class compaction
will not result in any (further) savings.EXAMPLE (this debug output is not part of this patch set):
- class size
- number of allocated objects
- number of used objects
- max objects per zspage
- pages per zspage
- estimated number of pages that will be freed[..]
class-512 objs:544 inuse:540 maxobj-per-zspage:8 pages-per-zspage:1 zspages-to-free:0
... class-512 compaction is useless. break
class-496 objs:660 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:2
class-496 objs:627 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:1
class-496 objs:594 inuse:570 maxobj-per-zspage:33 pages-per-zspage:4 zspages-to-free:0
... class-496 compaction is useless. break
class-448 objs:657 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:4
class-448 objs:648 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:3
class-448 objs:639 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:2
class-448 objs:630 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:1
class-448 objs:621 inuse:617 maxobj-per-zspage:9 pages-per-zspage:1 zspages-to-free:0
... class-448 compaction is useless. break
class-432 objs:728 inuse:685 maxobj-per-zspage:28 pages-per-zspage:3 zspages-to-free:1
class-432 objs:700 inuse:685 maxobj-per-zspage:28 pages-per-zspage:3 zspages-to-free:0
... class-432 compaction is useless. break
class-416 objs:819 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:2
class-416 objs:780 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:1
class-416 objs:741 inuse:705 maxobj-per-zspage:39 pages-per-zspage:4 zspages-to-free:0
... class-416 compaction is useless. break
class-400 objs:690 inuse:674 maxobj-per-zspage:10 pages-per-zspage:1 zspages-to-free:1
class-400 objs:680 inuse:674 maxobj-per-zspage:10 pages-per-zspage:1 zspages-to-free:0
... class-400 compaction is useless. break
class-384 objs:736 inuse:709 maxobj-per-zspage:32 pages-per-zspage:3 zspages-to-free:0
... class-384 compaction is useless. break
[..]Every "compaction is useless" indicates that we saved CPU cycles.
class-512 has
544 object allocated
540 objects used
8 objects per-pageEven if we have a ALMOST_EMPTY zspage, we still don't have enough room to
migrate all of its objects and free this zspage; so compaction will not
make a lot of sense, it's better to just leave it as is.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Always account per-class `zs_size_stat' stats. This data will help us
make better decisions during compaction. We are especially interested
in OBJ_ALLOCATED and OBJ_USED, which can tell us if class compaction
will result in any memory gain.For instance, we know the number of allocated objects in the class, the
number of objects being used (so we also know how many objects are not
used) and the number of objects per-page. So we can ensure if we have
enough unused objects to form at least one ZS_EMPTY zspage during
compaction.We calculate this value on per-class basis so we can calculate a total
number of zspages that can be released. Which is exactly what a
shrinker wants to know.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patchset tweaks compaction and makes it possible to trigger pool
compaction automatically when system is getting low on memory.zsmalloc in some cases can suffer from a notable fragmentation and
compaction can release some considerable amount of memory. The problem
here is that currently we fully rely on user space to perform compaction
when needed. However, performing zsmalloc compaction is not always an
obvious thing to do. For example, suppose we have a `idle' fragmented
(compaction was never performed) zram device and system is getting low
on memory due to some 3rd party user processes (gcc LTO, or firefox,
etc.). It's quite unlikely that user space will issue zpool compaction
in this case. Besides, user space cannot tell for sure how badly pool
is fragmented; however, this info is known to zsmalloc and, hence, to a
shrinker.This patch (of 7):
__zs_compact() does not use `nr_to_migrate', drop it.
Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Jun, 2015
2 commits
-
Remove zpool_evict() helper function. As zbud is currently the only
zpool implementation that supports eviction, add zpool and zpool_ops
references to struct zbud_pool and directly call zpool_ops->evict(zpool,
handle) on eviction.Currently zpool provides the zpool_evict helper which locks the zpool
list lock and searches through all pools to find the specific one
matching the caller, and call the corresponding zpool_ops->evict
function. However, this is unnecessary, as the zbud pool can simply
keep a reference to the zpool that created it, as well as the zpool_ops,
and directly call the zpool_ops->evict function, when it needs to evict
a page. This avoids a spinlock and list search in zpool for each
eviction.Signed-off-by: Dan Streetman
Cc: Seth Jennings
Cc: Minchan Kim
Cc: Nitin Gupta
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The DEBUG define in zsmalloc is useless, there is no usage of it at all.
Signed-off-by: Marcin Jabrzyk
Acked-by: Sergey Senozhatsky
Cc: Minchan Kim
Cc: Nitin Gupta
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Jun, 2015
1 commit
-
If zs_create_pool()->create_handle_cache()->kmem_cache_create() or
pool->name allocation fails, zs_create_pool()->destroy_handle_cache()
will dereference the NULL pool->handle_cachep.Modify destroy_handle_cache() to avoid this.
Signed-off-by: Sergey Senozhatsky
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Apr, 2015
12 commits
-
Do not perform cond_resched() before the busy compaction loop in
__zs_compact(), because this loop does it when needed.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Cc: Nitin Gupta
Cc: Stephen Rothwell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
There is no point in overriding the size class below. It causes fatal
corruption on the next chunk on the 3264-bytes size class, which is the
last size class that is not huge.For example, if the requested size was exactly 3264 bytes, current
zsmalloc allocates and returns a chunk from the size class of 3264 bytes,
not 4096. User access to this chunk may overwrite head of the next
adjacent chunk.Here is the panic log captured when freelist was corrupted due to this:
Kernel BUG at ffffffc00030659c [verbose debug info unavailable]
Internal error: Oops - BUG: 96000006 [#1] PREEMPT SMP
Modules linked in:
exynos-snapshot: core register saved(CPU:5)
CPUMERRSR: 0000000000000000, L2MERRSR: 0000000000000000
exynos-snapshot: context saved(CPU:5)
exynos-snapshot: item - log_kevents is disabled
CPU: 5 PID: 898 Comm: kswapd0 Not tainted 3.10.61-4497415-eng #1
task: ffffffc0b8783d80 ti: ffffffc0b71e8000 task.ti: ffffffc0b71e8000
PC is at obj_idx_to_offset+0x0/0x1c
LR is at obj_malloc+0x44/0xe8
pc : [] lr : [] pstate: a0000045
sp : ffffffc0b71eb790
x29: ffffffc0b71eb790 x28: ffffffc00204c000
x27: 000000000001d96f x26: 0000000000000000
x25: ffffffc098cc3500 x24: ffffffc0a13f2810
x23: ffffffc098cc3501 x22: ffffffc0a13f2800
x21: 000011e1a02006e3 x20: ffffffc0a13f2800
x19: ffffffbc02a7e000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000feb
x15: 0000000000000000 x14: 00000000a01003e3
x13: 0000000000000020 x12: fffffffffffffff0
x11: ffffffc08b264000 x10: 00000000e3a01004
x9 : ffffffc08b263fea x8 : ffffffc0b1e611c0
x7 : ffffffc000307d24 x6 : 0000000000000000
x5 : 0000000000000038 x4 : 000000000000011e
x3 : ffffffbc00003e90 x2 : 0000000000000cc0
x1 : 00000000d0100371 x0 : ffffffbc00003e90Reported-by: Sooyong Suk
Signed-off-by: Heesub Shin
Tested-by: Sooyong Suk
Acked-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In putback_zspage, we don't need to insert a zspage into list of zspage
in size_class again to just fix fullness group. We could do directly
without reinsertion so we could save some instuctions.Reported-by: Heesub Shin
Signed-off-by: Minchan Kim
Cc: Nitin Gupta
Cc: Sergey Senozhatsky
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Ganesh Mahendran
Cc: Luigi Semenzato
Cc: Gunho Lee
Cc: Juneho Choi
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
A micro-optimization. Avoid additional branching and reduce (a bit)
registry pressure (f.e. s_off += size; d_off += size; may be calculated
twise: first for >= PAGE_SIZE check and later for offset update in "else"
clause).scripts/bloat-o-meter shows some improvement
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
function old new delta
zs_object_copy 550 540 -10Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Cc: Nitin Gupta
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Do not synchronize rcu in zs_compact(). Neither zsmalloc not
zram use rcu.Signed-off-by: Sergey Senozhatsky
Acked-by: Minchan Kim
Cc: Nitin Gupta
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Yinghao Xie
Suggested-by: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Create zsmalloc doc which explains design concept and stat information.
Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
During investigating compaction, fullness information of each class is
helpful for investigating how the compaction works well. With that, we
could know how compaction works well more clear on each size class.Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We store handle on header of each allocated object so it increases the
size of each object by sizeof(unsigned long).If zram stores 4096 bytes to zsmalloc(ie, bad compression), zsmalloc needs
4104B-class to add handle.However, 4104B-class has 1-pages_per_zspage so wasted size by internal
fragment is 8192 - 4104, which is terrible.So this patch records the handle in page->private on such huge object(ie,
pages_per_zspage == 1 && maxobj_per_zspage == 1) instead of header of each
object so we could use 4096B-class, not 4104B-class.Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Curretly, zsmalloc regards a zspage as ZS_ALMOST_EMPTY if the zspage has
under 1/4 used objects(ie, fullness_threshold_frac). It could make result
in loose packing since zsmalloc migrates only ZS_ALMOST_EMPTY zspage out.This patch changes the rule so that zsmalloc makes zspage which has above
3/4 used object ZS_ALMOST_FULL so it could make tight packing.Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch provides core functions for migration of zsmalloc. Migraion
policy is simple as follows.for each size class {
while {
src_page = get zs_page from ZS_ALMOST_EMPTY
if (!src_page)
break;
dst_page = get zs_page from ZS_ALMOST_FULL
if (!dst_page)
dst_page = get zs_page from ZS_ALMOST_EMPTY
if (!dst_page)
break;
migrate(from src_page, to dst_page);
}
}For migration, we need to identify which objects in zspage are allocated
to migrate them out. We could know it by iterating of freed objects in a
zspage because first_page of zspage keeps free objects singly-linked list
but it's not efficient. Instead, this patch adds a tag(ie,
OBJ_ALLOCATED_TAG) in header of each object(ie, handle) so we could check
whether the object is allocated easily.This patch adds another status bit in handle to synchronize between user
access through zs_map_object and migration. During migration, we cannot
move objects user are using due to data coherency between old object and
new object.[akpm@linux-foundation.org: zsmalloc.c needs sched.h for cond_resched()]
Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In later patch, migration needs some part of functions in zs_malloc and
zs_free so this patch factor out them.Signed-off-by: Minchan Kim
Cc: Juneho Choi
Cc: Gunho Lee
Cc: Luigi Semenzato
Cc: Dan Streetman
Cc: Seth Jennings
Cc: Nitin Gupta
Cc: Jerome Marchand
Cc: Sergey Senozhatsky
Cc: Joonsoo Kim
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
