On Fri, 26 Feb 2010 21:30:15 +0900
Daisuke Nishimura <d-nishimura@xxxxxxxxxxxxxxxxx> wrote:
> On Fri, 26 Feb 2010 16:17:52 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > Okay. following is a candidate we can have. This will be incomplete until
> > we have oom notifier for memcg but may be better than miss-firing
> > page_fault_out_of_memory. Nishimura-san, how do you think this ?
> > (Added Andrew to CC.)
> >
> Thank you very much for your patch.
> I agree it's enough for quick fix, and it seems to work.
>
> > ==
> >
> > From: KAMEZAWA Hiroyuk <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> >
> > In current page-fault code,
> >
> > handle_mm_fault()
> > -> ...
> > -> mem_cgroup_charge()
> > -> map page or handle error.
> > -> check return code.
> >
> > If page fault's return code is VM_FAULT_OOM, page_fault_out_of_memory()
> > is called. But if it's caused by memcg, OOM should have been already
> > invoked.
> > Then, I added a patch: a636b327f731143ccc544b966cfd8de6cb6d72c6
> >
> > That patch records last_oom_jiffies for memcg's sub-hierarchy and
> > prevents page_fault_out_of_memory from being invoked in near future.
> >
> > But Nishimura-san reported that check by jiffies is not enough
> > when the system is terribly heavy.
> >
> > This patch changes memcg's oom logic as.
> > * If memcg causes OOM-kill, continue to retry.
> > * memcg hangs when there are no task to be killed.
> IIUC, this behavior is the same as current behavior. mem_cgroup_out_of_memory()
> hangs if all of the tasks in the cgroup are OOM_DISABLE'ed.
>
Ah, yes. I'll add that comment.
> > * remove jiffies check which is used now.
> >
> > TODO:
> > * add oom notifier for informing management daemon.
> > * more clever sleep logic for avoiding to use much CPU.
> >
> > Signed-off-by: KAMEZAWA Hiroyuk <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > ---
> > include/linux/memcontrol.h | 6 ----
> > mm/memcontrol.c | 56 ++++++++++++++++-----------------------------
> > mm/oom_kill.c | 28 ++++++++++++----------
> > 3 files changed, 37 insertions(+), 53 deletions(-)
> >
> > Index: mmotm-2.6.33-Feb11/include/linux/memcontrol.h
> > ===================================================================
> > --- mmotm-2.6.33-Feb11.orig/include/linux/memcontrol.h
> > +++ mmotm-2.6.33-Feb11/include/linux/memcontrol.h
> > @@ -124,7 +124,6 @@ static inline bool mem_cgroup_disabled(v
> > return false;
> > }
> >
> > -extern bool mem_cgroup_oom_called(struct task_struct *task);
> > void mem_cgroup_update_file_mapped(struct page *page, int val);
> > unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> > gfp_t gfp_mask, int nid,
> > @@ -258,11 +257,6 @@ static inline bool mem_cgroup_disabled(v
> > return true;
> > }
> >
> > -static inline bool mem_cgroup_oom_called(struct task_struct *task)
> > -{
> > - return false;
> > -}
> > -
> > static inline int
> > mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
> > {
> > 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
> > @@ -200,7 +200,6 @@ struct mem_cgroup {
> > * Should the accounting and control be hierarchical, per subtree?
> > */
> > bool use_hierarchy;
> > - unsigned long last_oom_jiffies;
> > atomic_t refcnt;
> >
> > unsigned int swappiness;
> > @@ -1234,34 +1233,6 @@ static int mem_cgroup_hierarchical_recla
> > return total;
> > }
> >
> > -
> > /*
> > * Currently used to update mapped file statistics, but the routine can be
> > * generalized to update other statistics as well.
> > @@ -1549,11 +1520,27 @@ static int __mem_cgroup_try_charge(struc
> > }
> >
> > if (!nr_retries--) {
> > - if (oom) {
> > - mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
> > - record_last_oom(mem_over_limit);
> > + if (!oom)
> > + goto nomem;
> > + mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
> > + /*
> > + * If killed someone, we can retry. If killed myself,
> > + * allow to go ahead in force.
> > + *
> > + * Note: There may be a case we can never kill any
> > + * processes under us.(by OOM_DISABLE) But, in that
> > + * case, if we return -ENOMEM, pagefault_out_of_memory
> > + * will kill someone innocent, out of this memcg.
> > + * So, what we can do is just try harder..
> > + */
> > + if (test_thread_flag(TIF_MEMDIE)) {
> Is "if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))" better
> to accept SIGKILL ?
>
Hmm, ok, will add that. One problem of TIF_MEMDIE is that it's added to a thread
not to a process.
> > + css_put(&mem->css);
> > + *memcg = NULL;
> > + return 0;
> > }
> > - goto nomem;
> > + /* give chance to run */
> > + schedule_timeout(1);
> > + nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> > }
> > }
> > if (csize > PAGE_SIZE)
> > @@ -2408,8 +2395,7 @@ void mem_cgroup_end_migration(struct mem
> >
> > /*
> > * A call to try to shrink memory usage on charge failure at shmem's swapin.
> > - * Calling hierarchical_reclaim is not enough because we should update
> > - * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
> > + * Calling hierarchical_reclaim is not enough. We may have to call OOM.
> > * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
> > * not from the memcg which this page would be charged to.
> > * try_charge_swapin does all of these works properly.
> > 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
> > @@ -466,27 +466,39 @@ static int oom_kill_process(struct task_
> > }
> >
> > #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > +/*
> > + * When select_bad_process() can't find proper process and we failed to
> > + * kill current, returns 0 as faiulre of OOM-kill. Otherwise, returns 1.
> > + */
> hmm, what function does this comment describe ?
> mem_cgroup_out_of_memory() returns void.
>
Ahhh, I'll remove this. This is garbage.
I'll clean up this and post as quick-fix.
Thanks,
-Kame
>
> Thanks,
> Daisuke Nishimura.
>
> > void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
> > {
> > unsigned long points = 0;
> > struct task_struct *p;
> > + int not_found = 0;
> >
> > if (sysctl_panic_on_oom == 2)
> > panic("out of memory(memcg). panic_on_oom is selected.\n");
> > read_lock(&tasklist_lock);
> > retry:
> > + not_found = 0;
> > p = select_bad_process(&points, mem);
> > if (PTR_ERR(p) == -1UL)
> > goto out;
> > -
> > - if (!p)
> > + if (!p) {
> > + not_found = 1;
> > p = current;
> > + printk(KERN_ERR "It seems there are no killable processes "
> > + "under memcg in OOM. Try to kill current\n");
> > + }
> >
> > if (oom_kill_process(p, gfp_mask, 0, points, mem,
> > - "Memory cgroup out of memory"))
> > - goto retry;
> > + "Memory cgroup out of memory")) {
> > + if (!not_found) /* some race with OOM_DISABLE etc ? */
> > + goto retry;
> > + }
> > out:
> > read_unlock(&tasklist_lock);
> > + /* Even if we don't kill any, give chance to try to recalim more */
> > }
> > #endif
> >
> > @@ -601,13 +613,6 @@ 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 +624,6 @@ 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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>
>
>
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