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SubjectRe: [RFC][PATCH v3 0/10] memcg async reclaim
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On Thu, May 26, 2011 at 9:49 PM, Ying Han <yinghan@google.com> wrote:
> On Thu, May 26, 2011 at 9:34 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>> On Thu, 26 May 2011 21:33:32 -0700
>> Ying Han <yinghan@google.com> wrote:
>>
>>> On Thu, May 26, 2011 at 7:16 PM, KAMEZAWA Hiroyuki
>>> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>> > On Thu, 26 May 2011 18:49:26 -0700
>>> > Ying Han <yinghan@google.com> wrote:
>>> >
>>> >> On Wed, May 25, 2011 at 10:10 PM, KAMEZAWA Hiroyuki
>>> >> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>> >> >
>>> >> > It's now merge window...I just dump my patch queue to hear other's idea.
>>> >> > I wonder I should wait until dirty_ratio for memcg is queued to mmotm...
>>> >> > I'll be busy with LinuxCon Japan etc...in the next week.
>>> >> >
>>> >> > This patch is onto mmotm-May-11 + some patches queued in mmotm, as numa_stat.
>>> >> >
>>> >> > This is a patch for memcg to keep margin to the limit in background.
>>> >> > By keeping some margin to the limit in background, application can
>>> >> > avoid foreground memory reclaim at charge() and this will help latency.
>>> >> >
>>> >> > Main changes from v2 is.
>>> >> >  - use SCHED_IDLE.
>>> >> >  - removed most of heuristic codes. Now, code is very simple.
>>> >> >
>>> >> > By using SCHED_IDLE, async memory reclaim can only consume 0.3%? of cpu
>>> >> > if the system is truely busy but can use much CPU if the cpu is idle.
>>> >> > Because my purpose is for reducing latency without affecting other running
>>> >> > applications, SCHED_IDLE fits this work.
>>> >> >
>>> >> > If application need to stop by some I/O or event, background memory reclaim
>>> >> > will cull memory while the system is idle.
>>> >> >
>>> >> > Perforemce:
>>> >> >  Running an httpd (apache) under 300M limit. And access 600MB working set
>>> >> >  with normalized distribution access by apatch-bench.
>>> >> >  apatch bench's concurrency was 4 and did 40960 accesses.
>>> >> >
>>> >> > Without async reclaim:
>>> >> > Connection Times (ms)
>>> >> >              min  mean[+/-sd] median   max
>>> >> > Connect:        0    0   0.0      0       2
>>> >> > Processing:    30   37  28.3     32    1793
>>> >> > Waiting:       28   35  25.5     31    1792
>>> >> > Total:         30   37  28.4     32    1793
>>> >> >
>>> >> > Percentage of the requests served within a certain time (ms)
>>> >> >  50%     32
>>> >> >  66%     32
>>> >> >  75%     33
>>> >> >  80%     34
>>> >> >  90%     39
>>> >> >  95%     60
>>> >> >  98%    100
>>> >> >  99%    133
>>> >> >  100%   1793 (longest request)
>>> >> >
>>> >> > With async reclaim:
>>> >> > Connection Times (ms)
>>> >> >              min  mean[+/-sd] median   max
>>> >> > Connect:        0    0   0.0      0       2
>>> >> > Processing:    30   35  12.3     32     678
>>> >> > Waiting:       28   34  12.0     31     658
>>> >> > Total:         30   35  12.3     32     678
>>> >> >
>>> >> > Percentage of the requests served within a certain time (ms)
>>> >> >  50%     32
>>> >> >  66%     32
>>> >> >  75%     33
>>> >> >  80%     34
>>> >> >  90%     39
>>> >> >  95%     49
>>> >> >  98%     71
>>> >> >  99%     86
>>> >> >  100%    678 (longest request)
>>> >> >
>>> >> >
>>> >> > It seems latency is stabilized by hiding memory reclaim.
>>> >> >
>>> >> > The score for memory reclaim was following.
>>> >> > See patch 10 for meaning of each member.
>>> >> >
>>> >> > == without async reclaim ==
>>> >> > recent_scan_success_ratio 44
>>> >> > limit_scan_pages 388463
>>> >> > limit_freed_pages 162238
>>> >> > limit_elapsed_ns 13852159231
>>> >> > soft_scan_pages 0
>>> >> > soft_freed_pages 0
>>> >> > soft_elapsed_ns 0
>>> >> > margin_scan_pages 0
>>> >> > margin_freed_pages 0
>>> >> > margin_elapsed_ns 0
>>> >> >
>>> >> > == with async reclaim ==
>>> >> > recent_scan_success_ratio 6
>>> >> > limit_scan_pages 0
>>> >> > limit_freed_pages 0
>>> >> > limit_elapsed_ns 0
>>> >> > soft_scan_pages 0
>>> >> > soft_freed_pages 0
>>> >> > soft_elapsed_ns 0
>>> >> > margin_scan_pages 1295556
>>> >> > margin_freed_pages 122450
>>> >> > margin_elapsed_ns 644881521
>>> >> >
>>> >> >
>>> >> > For this case, SCHED_IDLE workqueue can reclaim enough memory to the httpd.
>>> >> >
>>> >> > I may need to dig why scan_success_ratio is far different in the both case.
>>> >> > I guess the difference of epalsed_ns is because several threads enter
>>> >> > memory reclaim when async reclaim doesn't run. But may not...
>>> >> >
>>> >>
>>> >>
>>> >> Hmm.. I noticed a very strange behavior on a simple test w/ the patch set.
>>> >>
>>> >> Test:
>>> >> I created a 4g memcg and start doing cat. Then the memcg being OOM
>>> >> killed as soon as it reaches its hard_limit. We shouldn't hit OOM even
>>> >> w/o async-reclaim.
>>> >>
>>> >> Again, I will read through the patch. But like to post the test result first.
>>> >>
>>> >> $ echo $$ >/dev/cgroup/memory/A/tasks
>>> >> $ cat /dev/cgroup/memory/A/memory.limit_in_bytes
>>> >> 4294967296
>>> >>
>>> >> $ time cat /export/hdc3/dd_A/tf0 > /dev/zero
>>> >> Killed
>>> >>
>>> >
>>> > I did the same kind of test without any problem...but ok, I'll do more test
>>> > later.
>>> >
>>> >
>>> >
>>> >> real  0m53.565s
>>> >> user  0m0.061s
>>> >> sys   0m4.814s
>>> >>
>>> >> Here is the OOM log:
>>> >>
>>> >> May 26 18:43:00  kernel: [  963.489112] cat invoked oom-killer:
>>> >> gfp_mask=0xd0, order=0, oom_adj=0, oom_score_adj=0
>>> >> May 26 18:43:00  kernel: [  963.489121] Pid: 9425, comm: cat Tainted:
>>> >> G        W   2.6.39-mcg-DEV #131
>>> >> May 26 18:43:00  kernel: [  963.489123] Call Trace:
>>> >> May 26 18:43:00  kernel: [  963.489134]  [<ffffffff810e3512>]
>>> >> dump_header+0x82/0x1af
>>> >> May 26 18:43:00  kernel: [  963.489137]  [<ffffffff810e33ca>] ?
>>> >> spin_lock+0xe/0x10
>>> >> May 26 18:43:00  kernel: [  963.489140]  [<ffffffff810e33f9>] ?
>>> >> find_lock_task_mm+0x2d/0x67
>>> >> May 26 18:43:00  kernel: [  963.489143]  [<ffffffff810e38dd>]
>>> >> oom_kill_process+0x50/0x27b
>>> >> May 26 18:43:00  kernel: [  963.489155]  [<ffffffff810e3dc6>]
>>> >> mem_cgroup_out_of_memory+0x9a/0xe4
>>> >> May 26 18:43:00  kernel: [  963.489160]  [<ffffffff811153aa>]
>>> >> mem_cgroup_handle_oom+0x134/0x1fe
>>> >> May 26 18:43:00  kernel: [  963.489163]  [<ffffffff81114a72>] ?
>>> >> __mem_cgroup_insert_exceeded+0x83/0x83
>>> >> May 26 18:43:00  kernel: [  963.489176]  [<ffffffff811166e9>]
>>> >> __mem_cgroup_try_charge.clone.3+0x368/0x43a
>>> >> May 26 18:43:00  kernel: [  963.489179]  [<ffffffff81117586>]
>>> >> mem_cgroup_cache_charge+0x95/0x123
>>> >> May 26 18:43:00  kernel: [  963.489183]  [<ffffffff810e16d8>]
>>> >> add_to_page_cache_locked+0x42/0x114
>>> >> May 26 18:43:00  kernel: [  963.489185]  [<ffffffff810e17db>]
>>> >> add_to_page_cache_lru+0x31/0x5f
>>> >> May 26 18:43:00  kernel: [  963.489189]  [<ffffffff81145636>]
>>> >> mpage_readpages+0xb6/0x132
>>> >> May 26 18:43:00  kernel: [  963.489194]  [<ffffffff8119992f>] ?
>>> >> noalloc_get_block_write+0x24/0x24
>>> >> May 26 18:43:00  kernel: [  963.489197]  [<ffffffff8119992f>] ?
>>> >> noalloc_get_block_write+0x24/0x24
>>> >> May 26 18:43:00  kernel: [  963.489201]  [<ffffffff81036742>] ?
>>> >> __switch_to+0x160/0x212
>>> >> May 26 18:43:00  kernel: [  963.489205]  [<ffffffff811978b2>]
>>> >> ext4_readpages+0x1d/0x1f
>>> >> May 26 18:43:00  kernel: [  963.489209]  [<ffffffff810e8d4b>]
>>> >> __do_page_cache_readahead+0x144/0x1e3
>>> >> May 26 18:43:00  kernel: [  963.489212]  [<ffffffff810e8e0b>]
>>> >> ra_submit+0x21/0x25
>>> >> May 26 18:43:00  kernel: [  963.489215]  [<ffffffff810e9075>]
>>> >> ondemand_readahead+0x18c/0x19f
>>> >> May 26 18:43:00  kernel: [  963.489218]  [<ffffffff810e9105>]
>>> >> page_cache_async_readahead+0x7d/0x86
>>> >> May 26 18:43:00  kernel: [  963.489221]  [<ffffffff810e2b7e>]
>>> >> generic_file_aio_read+0x2d8/0x5fe
>>> >> May 26 18:43:00  kernel: [  963.489225]  [<ffffffff81119626>]
>>> >> do_sync_read+0xcb/0x108
>>> >> May 26 18:43:00  kernel: [  963.489230]  [<ffffffff811f168a>] ?
>>> >> fsnotify_perm+0x66/0x72
>>> >> May 26 18:43:00  kernel: [  963.489233]  [<ffffffff811f16f7>] ?
>>> >> security_file_permission+0x2e/0x33
>>> >> May 26 18:43:00  kernel: [  963.489236]  [<ffffffff8111a0c8>]
>>> >> vfs_read+0xab/0x107
>>> >> May 26 18:43:00  kernel: [  963.489239]  [<ffffffff8111a1e4>] sys_read+0x4a/0x6e
>>> >> May 26 18:43:00  kernel: [  963.489244]  [<ffffffff8140f469>]
>>> >> sysenter_dispatch+0x7/0x27
>>> >> May 26 18:43:00  kernel: [  963.489248] Task in /A killed as a result
>>> >> of limit of /A
>>> >> May 26 18:43:00  kernel: [  963.489251] memory: usage 4194304kB, limit
>>> >> 4194304kB, failcnt 26
>>> >> May 26 18:43:00  kernel: [  963.489253] memory+swap: usage 0kB, limit
>>> >> 9007199254740991kB, failcnt 0
>>> >>
>>> >
>>> > Hmm, why memory+swap usage 0kb here...
>>> >
>>> > In this set, I used mem_cgroup_margin() rather than res_counter_margin().
>>> > Hmm, do you disable swap accounting ? If so, I may miss some.
>>>
>>> Yes, I disabled the swap accounting in .config:
>>> # CONFIG_CGROUP_MEM_RES_CTLR_SWAP is not set
>>>
>>>
>>> Here is how i reproduce it:
>>>
>>> $ mkdir /dev/cgroup/memory/D
>>> $ echo 4g >/dev/cgroup/memory/D/memory.limit_in_bytes
>>>
>>> $ cat /dev/cgroup/memory/D/memory.limit_in_bytes
>>> 4294967296
>>>
>>> $ cat /dev/cgroup/memory/D/memory.
>>> memory.async_control             memory.max_usage_in_bytes
>>> memory.soft_limit_in_bytes       memory.use_hierarchy
>>> memory.failcnt                   memory.move_charge_at_immigrate
>>> memory.stat
>>> memory.force_empty               memory.oom_control
>>> memory.swappiness
>>> memory.limit_in_bytes            memory.reclaim_stat
>>> memory.usage_in_bytes
>>>
>>> $ cat /dev/cgroup/memory/D/memory.async_control
>>> 0
>>> $ echo 1 >/dev/cgroup/memory/D/memory.async_control
>>> $ cat /dev/cgroup/memory/D/memory.async_control
>>> 1
>>>
>>> $ echo $$ >/dev/cgroup/memory/D/tasks
>>> $ cat /proc/4358/cgroup
>>> 3:memory:/D
>>>
>>> $ time cat /export/hdc3/dd_A/tf0 > /dev/zero
>>> Killed
>>>
>>
>> If you applied my patches collectly, async_control can be seen if
>> swap controller is configured because of BUG in patch.
>
> I noticed the BUG at the very beginning, so all my tests are having the fix.
>
>>
>> I could cat 20G file under 4G limit without any problem with boot option
>> swapaccount=0. no problem if async_control == 0 ?
>
> $ cat /dev/cgroup/memory/D/memory.async_control
> 1
>
> I have the .config
> # CONFIG_CGROUP_MEM_RES_CTLR_SWAP is not set
>
> Not sure if that makes difference. I will test next to turn that on.

I know what's the problem and also verified. Our configuration might
differs on the "#if MAX_NUMNODES > 1"
Please apply the following patch:

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6a52699..0b88d71 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1217,7 +1217,7 @@ unsigned long
mem_cgroup_zone_reclaimable_pages(struct mem_cgroup *memcg,
struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);

nr = MEM_CGROUP_ZSTAT(mz, NR_ACTIVE_FILE) +
- MEM_CGROUP_ZSTAT(mz, NR_ACTIVE_FILE);
+ MEM_CGROUP_ZSTAT(mz, NR_INACTIVE_FILE);
if (nr_swap_pages > 0)
nr += MEM_CGROUP_ZSTAT(mz, NR_ACTIVE_ANON) +
MEM_CGROUP_ZSTAT(mz, NR_INACTIVE_ANON);
--Ying

>
> --Ying
>
>
>>
>>
>>
>> Thanks,
>> -Kame
>>
>>
>>
>>
>
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