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Date: Fri, 27 May 2011 11:16:39 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Ying Han <yinghan@...gle.com> Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>, "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com> Subject: Re: [RFC][PATCH v3 0/10] memcg async reclaim On Thu, 26 May 2011 18:49:26 -0700 Ying Han <yinghan@...gle.com> wrote: > On Wed, May 25, 2011 at 10:10 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@...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. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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