Messages in this thread Patch in this message | | | Date | Fri, 08 Feb 2013 10:40:13 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache_locked |
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(2013/02/07 20:01), Kamezawa Hiroyuki wrote: > (2013/02/06 23:01), Michal Hocko wrote: >> On Wed 06-02-13 02:17:21, azurIt wrote: >>>> 5-memcg-fix-1.patch is not complete. It doesn't contain the folloup I >>>> mentioned in a follow up email. Here is the full patch: >>> >>> >>> Here is the log where OOM, again, killed MySQL server [search for "(mysqld)"]: >>> http://www.watchdog.sk/lkml/oom_mysqld6 >> >> [...] >> WARNING: at mm/memcontrol.c:2409 T.1149+0x2d9/0x610() >> Hardware name: S5000VSA >> gfp_mask:4304 nr_pages:1 oom:0 ret:2 >> Pid: 3545, comm: apache2 Tainted: G W 3.2.37-grsec #1 >> Call Trace: >> [<ffffffff8105502a>] warn_slowpath_common+0x7a/0xb0 >> [<ffffffff81055116>] warn_slowpath_fmt+0x46/0x50 >> [<ffffffff81108163>] ? mem_cgroup_margin+0x73/0xa0 >> [<ffffffff8110b6f9>] T.1149+0x2d9/0x610 >> [<ffffffff812af298>] ? blk_finish_plug+0x18/0x50 >> [<ffffffff8110c6b4>] mem_cgroup_cache_charge+0xc4/0xf0 >> [<ffffffff810ca6bf>] add_to_page_cache_locked+0x4f/0x140 >> [<ffffffff810ca7d2>] add_to_page_cache_lru+0x22/0x50 >> [<ffffffff810cad32>] filemap_fault+0x252/0x4f0 >> [<ffffffff810eab18>] __do_fault+0x78/0x5a0 >> [<ffffffff810edcb4>] handle_pte_fault+0x84/0x940 >> [<ffffffff810e2460>] ? vma_prio_tree_insert+0x30/0x50 >> [<ffffffff810f2508>] ? vma_link+0x88/0xe0 >> [<ffffffff810ee6a8>] handle_mm_fault+0x138/0x260 >> [<ffffffff8102709d>] do_page_fault+0x13d/0x460 >> [<ffffffff810f46fc>] ? do_mmap_pgoff+0x3dc/0x430 >> [<ffffffff815b61ff>] page_fault+0x1f/0x30 >> ---[ end trace 8817670349022007 ]--- >> apache2 invoked oom-killer: gfp_mask=0x0, order=0, oom_adj=0, oom_score_adj=0 >> apache2 cpuset=uid mems_allowed=0 >> Pid: 3545, comm: apache2 Tainted: G W 3.2.37-grsec #1 >> Call Trace: >> [<ffffffff810ccd2e>] dump_header+0x7e/0x1e0 >> [<ffffffff810ccc2f>] ? find_lock_task_mm+0x2f/0x70 >> [<ffffffff810cd1f5>] oom_kill_process+0x85/0x2a0 >> [<ffffffff810cd8a5>] out_of_memory+0xe5/0x200 >> [<ffffffff810cda7d>] pagefault_out_of_memory+0xbd/0x110 >> [<ffffffff81026e76>] mm_fault_error+0xb6/0x1a0 >> [<ffffffff8102734e>] do_page_fault+0x3ee/0x460 >> [<ffffffff810f46fc>] ? do_mmap_pgoff+0x3dc/0x430 >> [<ffffffff815b61ff>] page_fault+0x1f/0x30 >> >> The first trace comes from the debugging WARN and it clearly points to >> a file fault path. __do_fault pre-charges a page in case we need to >> do CoW (copy-on-write) for the returned page. This one falls back to >> memcg OOM and never returns ENOMEM as I have mentioned earlier. >> However, the fs fault handler (filemap_fault here) can fallback to >> page_cache_read if the readahead (do_sync_mmap_readahead) fails >> to get page to the page cache. And we can see this happening in >> the first trace. page_cache_read then calls add_to_page_cache_lru >> and eventually gets to add_to_page_cache_locked which calls >> mem_cgroup_cache_charge_no_oom so we will get ENOMEM if oom should >> happen. This ENOMEM gets to the fault handler and kaboom. >> > > Hmm. do we need to increase the "limit" virtually at memcg oom until > the oom-killed process dies ?
Here is my naive idea... == From 1a46318cf89e7df94bd4844f29105b61dacf335b Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Date: Fri, 8 Feb 2013 10:43:52 +0900 Subject: [PATCH] [Don't Apply][PATCH] memcg relax resource at OOM situation.
When an OOM happens, a task is killed and resources will be freed.
A problem here is that a task, which is oom-killed, may wait for some other resource in which memory resource is required. Some thread waits for free memory may holds some mutex and oom-killed process wait for the mutex.
To avoid this, relaxing charged memory by giving virtual resource can be a help. The system can get back it at uncharge(). This is a sample native implementation.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 73 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 25ac5f4..4dea49a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -301,6 +301,9 @@ struct mem_cgroup { /* set when res.limit == memsw.limit */ bool memsw_is_minimum; + /* extra resource at emergency situation */ + unsigned long loan; + spinlock_t loan_lock; /* protect arrays of thresholds */ struct mutex thresholds_lock; @@ -2034,6 +2037,61 @@ static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg, mem_cgroup_iter_break(root_memcg, victim); return total; } +/* + * When a memcg is in OOM situation, this lack of resource may cause deadlock + * because of complicated lock dependency(i_mutex...). To avoid that, we + * need extra resource or avoid charging. + * + * A memcg can request resource in an emergency state. We call it as loan. + * A memcg will return a loan when it does uncharge resource. We disallow + * double-loan and moving task to other groups until the loan is fully + * returned. + * + * Note: the problem here is that we cannot know what amount resouce should + * be necessary to exiting an emergency state..... + */ +#define LOAN_MAX (2 * 1024 * 1024) + +static void mem_cgroup_make_loan(struct mem_cgroup *memcg) +{ + u64 usage; + unsigned long amount; + + amount = LOAN_MAX; + + usage = res_counter_read_u64(&memcg->res, RES_USAGE); + if (amount > usage /2 ) + amount = usage / 2; + spin_lock(&memcg->loan_lock); + if (memcg->loan) { + spin_unlock(&memcg->loan_lock); + return; + } + memcg->loan = amount; + res_counter_uncharge(&memcg->res, amount); + if (do_swap_account) + res_counter_uncharge(&memcg->memsw, amount); + spin_unlock(&memcg->loan_lock); +} + +/* return amount of free resource which can be uncharged */ +static unsigned long +mem_cgroup_may_return_loan(struct mem_cgroup *memcg, unsigned long val) +{ + unsigned long tmp; + /* we don't care small race here */ + if (unlikely(!memcg->loan)) + return val; + spin_lock(&memcg->loan_lock); + if (memcg->loan) { + tmp = min(memcg->loan, val); + memcg->loan -= tmp; + val -= tmp; + } + spin_unlock(&memcg->loan_lock); + return val; +} + /* * Check OOM-Killer is already running under our hierarchy. @@ -2182,6 +2240,7 @@ static bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask, if (need_to_kill) { finish_wait(&memcg_oom_waitq, &owait.wait); mem_cgroup_out_of_memory(memcg, mask, order); + mem_cgroup_make_loan(memcg); } else { schedule(); finish_wait(&memcg_oom_waitq, &owait.wait); @@ -2748,6 +2807,8 @@ static void __mem_cgroup_cancel_charge(struct mem_cgroup *memcg, if (!mem_cgroup_is_root(memcg)) { unsigned long bytes = nr_pages * PAGE_SIZE; + bytes = mem_cgroup_may_return_loan(memcg, bytes); + res_counter_uncharge(&memcg->res, bytes); if (do_swap_account) res_counter_uncharge(&memcg->memsw, bytes); @@ -3989,6 +4050,7 @@ static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg, { struct memcg_batch_info *batch = NULL; bool uncharge_memsw = true; + unsigned long val; /* If swapout, usage of swap doesn't decrease */ if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) @@ -4029,9 +4091,11 @@ static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg, batch->memsw_nr_pages++; return; direct_uncharge: - res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE); + val = nr_pages * PAGE_SIZE; + val = mem_cgroup_may_return_loan(memcg, val); + res_counter_uncharge(&memcg->res, val); if (uncharge_memsw) - res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE); + res_counter_uncharge(&memcg->memsw, val); if (unlikely(batch->memcg != memcg)) memcg_oom_recover(memcg); } @@ -4182,6 +4246,7 @@ void mem_cgroup_uncharge_start(void) void mem_cgroup_uncharge_end(void) { struct memcg_batch_info *batch = ¤t->memcg_batch; + unsigned long val; if (!batch->do_batch) return; @@ -4192,16 +4257,16 @@ void mem_cgroup_uncharge_end(void) if (!batch->memcg) return; + val = batch->nr_pages * PAGE_SIZE; + val = mem_cgroup_may_return_loan(batch->memcg, val); /* * This "batch->memcg" is valid without any css_get/put etc... * bacause we hide charges behind us. */ if (batch->nr_pages) - res_counter_uncharge(&batch->memcg->res, - batch->nr_pages * PAGE_SIZE); + res_counter_uncharge(&batch->memcg->res, val); if (batch->memsw_nr_pages) - res_counter_uncharge(&batch->memcg->memsw, - batch->memsw_nr_pages * PAGE_SIZE); + res_counter_uncharge(&batch->memcg->memsw, val); memcg_oom_recover(batch->memcg); /* forget this pointer (for sanity check) */ batch->memcg = NULL; @@ -6291,6 +6356,8 @@ mem_cgroup_css_alloc(struct cgroup *cont) memcg->move_charge_at_immigrate = 0; mutex_init(&memcg->thresholds_lock); spin_lock_init(&memcg->move_lock); + memcg->loan = 0; + spin_lock_init(&memcg->loan_lock); return &memcg->css; -- 1.7.10.2
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