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zram_meta_alloc could fail so caller should check it. Otherwise, your
system will hang.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Finally, we separated zram->lock dependency from 32bit stat/ table
handling so there is no reason to use rw_semaphore between read and
write path so this patch removes the lock from read path totally and
changes rw_semaphore with mutex. So, we could do
old:
read-read: OK
read-write: NO
write-write: NO
Now:
read-read: OK
read-write: OK
write-write: NO
The below data proves mixed workload performs well 11 times and there is
also enhance on write-write path because current rw-semaphore doesn't
support SPIN_ON_OWNER. It's side effect but anyway good thing for us.
Write-related tests perform better (from 61% to 1058%) but read path has
good/bad(from -2.22% to 1.45%) but they are all marginal within stddev.
CPU 12
iozone -t -T -l 12 -u 12 -r 16K -s 60M -I +Z -V 0
==Initial write ==Initial write
records: 10 records: 10
avg: 516189.16 avg: 839907.96
std: 22486.53 (4.36%) std: 47902.17 (5.70%)
max: 546970.60 max: 909910.35
min: 481131.54 min: 751148.38
==Rewrite ==Rewrite
records: 10 records: 10
avg: 509527.98 avg: 1050156.37
std: 45799.94 (8.99%) std: 40695.44 (3.88%)
max: 611574.27 max: 1111929.26
min: 443679.95 min: 980409.62
==Read ==Read
records: 10 records: 10
avg: 4408624.17 avg: 4472546.76
std: 281152.61 (6.38%) std: 163662.78 (3.66%)
max: 4867888.66 max: 4727351.03
min: 4058347.69 min: 4126520.88
==Re-read ==Re-read
records: 10 records: 10
avg: 4462147.53 avg: 4363257.75
std: 283546.11 (6.35%) std: 247292.63 (5.67%)
max: 4912894.44 max: 4677241.75
min: 4131386.50 min: 4035235.84
==Reverse Read ==Reverse Read
records: 10 records: 10
avg: 4565865.97 avg: 4485818.08
std: 313395.63 (6.86%) std: 248470.10 (5.54%)
max: 5232749.16 max: 4789749.94
min: 4185809.62 min: 3963081.34
==Stride read ==Stride read
records: 10 records: 10
avg: 4515981.80 avg: 4418806.01
std: 211192.32 (4.68%) std: 212837.97 (4.82%)
max: 4889287.28 max: 4686967.22
min: 4210362.00 min: 4083041.84
==Random read ==Random read
records: 10 records: 10
avg: 4410525.23 avg: 4387093.18
std: 236693.22 (5.37%) std: 235285.23 (5.36%)
max: 4713698.47 max: 4669760.62
min: 4057163.62 min: 3952002.16
==Mixed workload ==Mixed workload
records: 10 records: 10
avg: 243234.25 avg: 2818677.27
std: 28505.07 (11.72%) std: 195569.70 (6.94%)
max: 288905.23 max: 3126478.11
min: 212473.16 min: 2484150.69
==Random write ==Random write
records: 10 records: 10
avg: 555887.07 avg: 1053057.79
std: 70841.98 (12.74%) std: 35195.36 (3.34%)
max: 683188.28 max: 1096125.73
min: 437299.57 min: 992481.93
==Pwrite ==Pwrite
records: 10 records: 10
avg: 501745.93 avg: 810363.09
std: 16373.54 (3.26%) std: 19245.01 (2.37%)
max: 518724.52 max: 833359.70
min: 464208.73 min: 765501.87
==Pread ==Pread
records: 10 records: 10
avg: 4539894.60 avg: 4457680.58
std: 197094.66 (4.34%) std: 188965.60 (4.24%)
max: 4877170.38 max: 4689905.53
min: 4226326.03 min: 4095739.72
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit a0c516cbfc74 ("zram: don't grab mutex in zram_slot_free_noity")
introduced free request pending code to avoid scheduling by mutex under
spinlock and it was a mess which made code lenghty and increased
overhead.
Now, we don't need zram->lock any more to free slot so this patch
reverts it and then, tb_lock should protect it.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Currently, the zram table is protected by zram->lock but it's rather
coarse-grained lock and it makes hard for scalibility.
Let's use own rwlock instead of depending on zram->lock. This patch
adds new locking so obviously, it would make slow but this patch is just
prepartion for removing coarse-grained rw_semaphore(ie, zram->lock)
which is hurdle about zram scalability.
Final patch in this patchset series will remove the lock from read-path
and change rw_semaphore with mutex in write path. With bonus, we could
drop pending slot free mess in next patch.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Some of fields in zram->stats are protected by zram->lock which is
rather coarse-grained so let's use atomic operation without explict
locking.
This patch is ready for removing dependency of zram->lock in read path
which is very coarse-grained rw_semaphore. Of course, this patch adds
new atomic operation so it might make slow but my 12CPU test couldn't
spot any regression. All gain/lose is marginal within stddev.
iozone -t -T -l 12 -u 12 -r 16K -s 60M -I +Z -V 0
==Initial write ==Initial write
records: 50 records: 50
avg: 412875.17 avg: 415638.23
std: 38543.12 (9.34%) std: 36601.11 (8.81%)
max: 521262.03 max: 502976.72
min: 343263.13 min: 351389.12
==Rewrite ==Rewrite
records: 50 records: 50
avg: 416640.34 avg: 397914.33
std: 60798.92 (14.59%) std: 46150.42 (11.60%)
max: 543057.07 max: 522669.17
min: 304071.67 min: 316588.77
==Read ==Read
records: 50 records: 50
avg: 4147338.63 avg: 4070736.51
std: 179333.25 (4.32%) std: 223499.89 (5.49%)
max: 4459295.28 max: 4539514.44
min: 3753057.53 min: 3444686.31
==Re-read ==Re-read
records: 50 records: 50
avg: 4096706.71 avg: 4117218.57
std: 229735.04 (5.61%) std: 171676.25 (4.17%)
max: 4430012.09 max: 4459263.94
min: 2987217.80 min: 3666904.28
==Reverse Read ==Reverse Read
records: 50 records: 50
avg: 4062763.83 avg: 4078508.32
std: 186208.46 (4.58%) std: 172684.34 (4.23%)
max: 4401358.78 max: 4424757.22
min: 3381625.00 min: 3679359.94
==Stride read ==Stride read
records: 50 records: 50
avg: 4094933.49 avg: 4082170.22
std: 185710.52 (4.54%) std: 196346.68 (4.81%)
max: 4478241.25 max: 4460060.97
min: 3732593.23 min: 3584125.78
==Random read ==Random read
records: 50 records: 50
avg: 4031070.04 avg: 4074847.49
std: 192065.51 (4.76%) std: 206911.33 (5.08%)
max: 4356931.16 max: 4399442.56
min: 3481619.62 min: 3548372.44
==Mixed workload ==Mixed workload
records: 50 records: 50
avg: 149925.73 avg: 149675.54
std: 7701.26 (5.14%) std: 6902.09 (4.61%)
max: 191301.56 max: 175162.05
min: 133566.28 min: 137762.87
==Random write ==Random write
records: 50 records: 50
avg: 404050.11 avg: 393021.47
std: 58887.57 (14.57%) std: 42813.70 (10.89%)
max: 601798.09 max: 524533.43
min: 325176.99 min: 313255.34
==Pwrite ==Pwrite
records: 50 records: 50
avg: 411217.70 avg: 411237.96
std: 43114.99 (10.48%) std: 33136.29 (8.06%)
max: 530766.79 max: 471899.76
min: 320786.84 min: 317906.94
==Pread ==Pread
records: 50 records: 50
avg: 4154908.65 avg: 4087121.92
std: 151272.08 (3.64%) std: 219505.04 (5.37%)
max: 4459478.12 max: 4435857.38
min: 3730512.41 min: 3101101.67
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit a0c516cbfc74 ("zram: don't grab mutex in zram_slot_free_noity")
introduced pending zram slot free in zram's write path in case of
missing slot free by memory allocation failure in zram_slot_free_notify
but it is not necessary because we have already freed the slot right
before overwriting.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Sergey reported we don't need to handle pending free request every I/O
so that this patch removes it in read path while we remain it in write
path.
Let's consider below example.
Swap subsystem ask to zram "A" block free by swap_slot_free_notify but
zram had been pended it without real freeing. Swap subsystem allocates
"A" block for new data but request pended for a long time just handled
and zram blindly free new data on the "A" block. :(
That's why we couldn't remove handle pending free request right before
zram-write.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Dan and Sergey reported that there is a racy between reset and flushing
of pending work so that it could make oops by freeing zram->meta in
reset while zram_slot_free can access zram->meta if new request is
adding during the race window.
This patch moves flush after taking init_lock so it prevents new request
so that it closes the race.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add my copyright to the zram source code which I maintain.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove the old private compcache project address so upcoming patches
should be sent to LKML because we Linux kernel community will take care.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Zram has lived in staging for a LONG LONG time and have been
fixed/improved by many contributors so code is clean and stable now. Of
course, there are lots of product using zram in real practice.
The major TV companys have used zram as swap since two years ago and
recently our production team released android smart phone with zram
which is used as swap, too and recently Android Kitkat start to use zram
for small memory smart phone. And there was a report Google released
their ChromeOS with zram, too and cyanogenmod have been used zram long
time ago. And I heard some disto have used zram block device for tmpfs.
In addition, I saw many report from many other peoples. For example,
Lubuntu start to use it.
The benefit of zram is very clear. With my experience, one of the
benefit was to remove jitter of video application with backgroud memory
pressure. It would be effect of efficient memory usage by compression
but more issue is whether swap is there or not in the system. Recent
mobile platforms have used JAVA so there are many anonymous pages. But
embedded system normally are reluctant to use eMMC or SDCard as swap
because there is wear-leveling and latency issues so if we do not use
swap, it means we can't reclaim anoymous pages and at last, we could
encounter OOM kill. :(
Although we have real storage as swap, it was a problem, too. Because
it sometime ends up making system very unresponsible caused by slow swap
storage performance.
Quote from Luigi on Google
"Since Chrome OS was mentioned: the main reason why we don't use swap
to a disk (rotating or SSD) is because it doesn't degrade gracefully
and leads to a bad interactive experience. Generally we prefer to
manage RAM at a higher level, by transparently killing and restarting
processes. But we noticed that zram is fast enough to be competitive
with the latter, and it lets us make more efficient use of the
available RAM. " and he announced.
http://www.spinics.net/lists/linux-mm/msg57717.html
Other uses case is to use zram for block device. Zram is block device
so anyone can format the block device and mount on it so some guys on
the internet start zram as /var/tmp.
http://forums.gentoo.org/viewtopic-t-838198-start-0.html
Let's promote zram and enhance/maintain it instead of removing.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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