Tetsuo Handa wrote: > Michal Hocko wrote: > > > Therefore, this patch allows OOM victims to use ALLOC_OOM watermark for > > > last second allocation attempt. > > > > This changelog doesn't explain the problem, nor does it say why it > > should help. I would even argue that mentioning the LTP test is more > > confusing than helpful (also considering it a fix for 696453e66630ad45) > > because granting access to memory reserves will only help partially. > > I know granting access to memory reserves will only help partially. > The intent of granting access to memory reserves is to reduce needlessly > OOM killing more victims. > > > Anyway, the patch makes some sense to me but I am not going to ack it > > with a misleading changelog. > > > > Apart from how the changelog will look like, below is an updated patch > which to some degree recovers > > * That thread will now get access to memory reserves since it has a > * pending fatal signal. > > comment. It is pity that we will need to run more instructions in the fastpath > of __alloc_pages_slowpath() compared to "current->oom_kill_free_check_raced" > at out_of_memory(). Is this direction acceptable? If http://lkml.kernel.org/r/20171219114012.GK2787@xxxxxxxxxxxxxx , is direction below acceptable? > > --- > mm/page_alloc.c | 53 ++++++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 40 insertions(+), 13 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 31c1a61..f7bd969 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3334,6 +3334,10 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) > return page; > } > > +static struct page *alloc_pages_before_oomkill(gfp_t gfp_mask, > + unsigned int order, > + const struct alloc_context *ac); > + > static inline struct page * > __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, > const struct alloc_context *ac, unsigned long *did_some_progress) > @@ -3359,16 +3363,7 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) > return NULL; > } > > - /* > - * Go through the zonelist yet one more time, keep very high watermark > - * here, this is only to catch a parallel oom killing, we must fail if > - * we're still under heavy pressure. But make sure that this reclaim > - * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY > - * allocation which will never fail due to oom_lock already held. > - */ > - page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) & > - ~__GFP_DIRECT_RECLAIM, order, > - ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac); > + page = alloc_pages_before_oomkill(gfp_mask, order, ac); > if (page) > goto out; > > @@ -3734,9 +3729,17 @@ static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac) > return alloc_flags; > } > > -static bool oom_reserves_allowed(struct task_struct *tsk) > +static bool oom_reserves_allowed(void) > { > - if (!tsk_is_oom_victim(tsk)) > + struct mm_struct *mm = current->mm; > + > + if (!mm) > + mm = current->signal->oom_mm; > + /* MMF_OOM_VICTIM not set on mm means that I am not an OOM victim. */ > + if (!mm || !test_bit(MMF_OOM_VICTIM, &mm->flags)) > + return false; > + /* MMF_OOM_VICTIM can be set on mm used by the global init process. */ > + if (!fatal_signal_pending(current) && !(current->flags & PF_EXITING)) > return false; > > /* > @@ -3764,7 +3767,7 @@ static inline int __gfp_pfmemalloc_flags(gfp_t gfp_mask) > if (!in_interrupt()) { > if (current->flags & PF_MEMALLOC) > return ALLOC_NO_WATERMARKS; > - else if (oom_reserves_allowed(current)) > + else if (oom_reserves_allowed()) > return ALLOC_OOM; > } > > @@ -3776,6 +3779,30 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) > return !!__gfp_pfmemalloc_flags(gfp_mask); > } > > +static struct page *alloc_pages_before_oomkill(gfp_t gfp_mask, > + unsigned int order, > + const struct alloc_context *ac) > +{ > + /* > + * Go through the zonelist yet one more time, keep very high watermark > + * here, this is only to catch a parallel oom killing, we must fail if > + * we're still under heavy pressure. But make sure that this reclaim > + * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY > + * allocation which will never fail due to oom_lock already held. > + * Also, make sure that OOM victims can try ALLOC_OOM watermark > + * in case they haven't tried ALLOC_OOM watermark. > + */ > + int alloc_flags = ALLOC_CPUSET | ALLOC_WMARK_HIGH; > + int reserve_flags; > + > + gfp_mask |= __GFP_HARDWALL; > + gfp_mask &= ~__GFP_DIRECT_RECLAIM; > + reserve_flags = __gfp_pfmemalloc_flags(gfp_mask); > + if (reserve_flags) > + alloc_flags = reserve_flags; > + return get_page_from_freelist(gfp_mask, order, alloc_flags, ac); > +} > + > /* > * Checks whether it makes sense to retry the reclaim to make a forward progress > * for the given allocation request. > -- > 1.8.3.1 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . 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