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Date: Tue, 23 Feb 2010 14:02:18 +0900
From: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
rientjes@...gle.com, "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC][PATCH] memcg: page fault oom improvement
On Tue, 23 Feb 2010 12:03:15 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> Nishimura-san, could you review and test your extreme test case with this ?
>
Thank you for your patch.
I don't know why, but the problem seems not so easy to cause in mmotm as in 2.6.32.8,
but I'll try more anyway.
A few comments are inlined.
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> Now, because of page_fault_oom_kill, returning VM_FAULT_OOM means
> random oom-killer should be called. Considering memcg, it handles
> OOM-kill in its own logic, there was a problem as "oom-killer called
> twice" problem.
>
> By commit a636b327f731143ccc544b966cfd8de6cb6d72c6, I added a check
> in pagefault_oom_killer shouldn't kill some (random) task if
> memcg's oom-killer already killed anyone.
> That was done by comapring current jiffies and last oom jiffies of memcg.
>
> I thought that easy fix was enough, but Nishimura could write a test case
> where checking jiffies is not enough. So, my fix was not enough.
> This is a fix of above commit.
>
> This new one does this.
> * memcg's try_charge() never returns -ENOMEM if oom-killer is allowed.
> * If someone is calling oom-killer, wait for it in try_charge().
> * If TIF_MEMDIE is set as a result of try_charge(), return 0 and
> allow process to make progress (and die.)
> * removed hook in pagefault_out_of_memory.
>
> By this, pagefult_out_of_memory will be never called if memcg's oom-killer
> is called and scattered codes are now in memcg's charge logic again.
>
> TODO:
> If __GFP_WAIT is not specified in gfp_mask flag, VM_FAULT_OOM will return
> anyway. We need to investigate it whether there is a case.
>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Balbir Singh <balbir@...ibm.com>
> Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
> mm/memcontrol.c | 41 +++++++++++++++++++++++------------------
> mm/oom_kill.c | 11 +++--------
> 2 files changed, 26 insertions(+), 26 deletions(-)
>
> Index: mmotm-2.6.33-Feb11/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.33-Feb11.orig/mm/memcontrol.c
> +++ mmotm-2.6.33-Feb11/mm/memcontrol.c
> @@ -1234,21 +1234,12 @@ static int mem_cgroup_hierarchical_recla
> return total;
> }
>
> -bool mem_cgroup_oom_called(struct task_struct *task)
> +DEFINE_MUTEX(memcg_oom_mutex);
it can be static.
> +bool mem_cgroup_oom_called(struct mem_cgroup *mem)
> {
> - bool ret = false;
> - struct mem_cgroup *mem;
> - struct mm_struct *mm;
> -
> - rcu_read_lock();
> - mm = task->mm;
> - if (!mm)
> - mm = &init_mm;
> - mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
> - if (mem && time_before(jiffies, mem->last_oom_jiffies + HZ/10))
> - ret = true;
> - rcu_read_unlock();
> - return ret;
> + if (time_before(jiffies, mem->last_oom_jiffies + HZ/10))
> + return true;
> + return false;
> }
>
> static int record_last_oom_cb(struct mem_cgroup *mem, void *data)
> @@ -1549,11 +1540,25 @@ static int __mem_cgroup_try_charge(struc
> }
>
> if (!nr_retries--) {
> - if (oom) {
> - mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
> + int oom_kill_called;
> + if (!oom)
> + goto nomem;
> + mutex_lock(&memcg_oom_mutex);
> + oom_kill_called = mem_cgroup_oom_called(mem_over_limit);
> + if (!oom_kill_called)
> record_last_oom(mem_over_limit);
> - }
> - goto nomem;
> + mutex_unlock(&memcg_oom_mutex);
> + if (!oom_kill_called)
> + mem_cgroup_out_of_memory(mem_over_limit,
> + gfp_mask);
> + else /* give a chance to die for other tasks */
> + schedule_timeout(1);
> + nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + /* Killed myself ? */
> + if (!test_thread_flag(TIF_MEMDIE))
> + continue;
> + /* For smooth oom-kill of current, return 0 */
> + return 0;
> }
> }
> if (csize > PAGE_SIZE)
> Index: mmotm-2.6.33-Feb11/mm/oom_kill.c
> ===================================================================
> --- mmotm-2.6.33-Feb11.orig/mm/oom_kill.c
> +++ mmotm-2.6.33-Feb11/mm/oom_kill.c
> @@ -487,6 +487,9 @@ retry:
> goto retry;
> out:
> read_unlock(&tasklist_lock);
> + /* give a chance to die for selected process */
> + if (test_thread_flag(TIF_MEMDIE))
> + schedule_timeout_uninterruptible(1);
> }
> #endif
>
I think it should be "if (!test_thread_flag(TIF_MEMDIE))".
Thanks,
Daisuke Nishimura.
> @@ -601,13 +604,6 @@ void pagefault_out_of_memory(void)
> /* Got some memory back in the last second. */
> return;
>
> - /*
> - * If this is from memcg, oom-killer is already invoked.
> - * and not worth to go system-wide-oom.
> - */
> - if (mem_cgroup_oom_called(current))
> - goto rest_and_return;
> -
> if (sysctl_panic_on_oom)
> panic("out of memory from page fault. panic_on_oom is selected.\n");
>
> @@ -619,7 +615,6 @@ void pagefault_out_of_memory(void)
> * Give "p" a good chance of killing itself before we
> * retry to allocate memory.
> */
> -rest_and_return:
> if (!test_thread_flag(TIF_MEMDIE))
> schedule_timeout_uninterruptible(1);
> }
>
--
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