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Date: Thu, 26 May 2011 18:49:26 -0700 From: Ying Han <yinghan@...gle.com> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.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 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 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 --Ying > > 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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