From: Minchan Kim <minchan@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
mhocko@suse.com, joaodias@google.com
Subject: Re: [PATCH] mm: be more verbose for alloc_contig_range faliures
Date: Wed, 17 Feb 2021 09:45:27 -0800 [thread overview]
Message-ID: <YC1WN1rQONAnt5M9@google.com> (raw)
In-Reply-To: <0f201a5a-caaf-2861-59f2-b66152fe9c53@redhat.com>
On Wed, Feb 17, 2021 at 06:34:13PM +0100, David Hildenbrand wrote:
> On 17.02.21 18:26, Minchan Kim wrote:
> > On Wed, Feb 17, 2021 at 05:51:27PM +0100, David Hildenbrand wrote:
> > > On 17.02.21 17:36, Minchan Kim wrote:
> > > > alloc_contig_range is usually used on cma area or movable zone.
> > > > It's critical if the page migration fails on those areas so
> > > > dump more debugging message like memory_hotplug unless user
> > > > specifiy __GFP_NOWARN.
> > > >
> > > > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > > > ---
> > > > mm/page_alloc.c | 16 +++++++++++++++-
> > > > 1 file changed, 15 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > > index 0b55c9c95364..67f3ee3a1528 100644
> > > > --- a/mm/page_alloc.c
> > > > +++ b/mm/page_alloc.c
> > > > @@ -8486,6 +8486,15 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
> > > > NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
> > > > }
> > > > if (ret < 0) {
> > > > + if (!(cc->gfp_mask & __GFP_NOWARN)) {
> > > > + struct page *page;
> > > > +
> > > > + list_for_each_entry(page, &cc->migratepages, lru) {
> > > > + pr_warn("migrating pfn %lx failed ret:%d ",
> > > > + page_to_pfn(page), ret);
> > > > + dump_page(page, "migration failure");
> > > > + }
> > >
> > > This can create *a lot* of noise. For example, until huge pages are actually
> > > considered, we will choke on each end every huge page - and might do so over
> > > and over again.
> >
> > I am not familiar with huge page status at this moment but why couldn't
> > they use __GFP_NOWARN if they are supposed to fail frequently?
>
> any alloc_contig_range() user will fail on hugetlbfs pages right now when
> they are placed into CMA/ZONE_MOVABLE. Oscar is working on that upstream.
Until then, how about adding this under !CONFIG_HUGETLBFS?
>
> >
> > >
> > > This might be helpful for debugging, but is unacceptable for production
> > > systems for now I think. Maybe for now, do it based on CONFIG_DEBUG_VM.
> >
> > If it's due to huge page you mentioned above and caller passes
> > __GFP_NOWARN in that case, couldn't we enable always-on?
>
> It would make sense to add that for virito-mem when calling
> alloc_contig_range(). For now I didn't do so, because there were not that
> many messages yet - alloc_contig_range() essentially didn't understand
> __GFP_NOWARN.
>
> We should then also stop printing the "PFNs busy ..." part from
> alloc_contig_range() with __GFP_NOWARN.
Yub.
>
> >
> > Actually, I am targeting cma allocation failure, which should
> > be rather rare compared to other call sites but critical to fail.
> > If it's concern to emit too many warning message, I will scope
> > down for site for only cma allocation.
>
> If you add "__GFP_NOWARN" when !ZONE_MOVABLE, how would you ever print
> something for CMA? What am I missing? CMA is usually not on ZONE_MOVABLE.
If the caller of cma_alloc passed __GFP_NOWARN, I don't care since
caller explictly declare it's not critical. What I'd like to catch up
is cma_alloc with !__GFP_NOWARN sites.
next prev parent reply other threads:[~2021-02-17 17:45 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 16:36 [PATCH] mm: be more verbose for alloc_contig_range faliures Minchan Kim
2021-02-17 16:51 ` David Hildenbrand
2021-02-17 17:26 ` Minchan Kim
2021-02-17 17:34 ` David Hildenbrand
2021-02-17 17:45 ` Minchan Kim [this message]
2021-02-18 8:56 ` Michal Hocko
2021-02-18 9:02 ` David Hildenbrand
2021-02-18 9:35 ` Michal Hocko
2021-02-18 9:43 ` David Hildenbrand
2021-02-18 9:59 ` Michal Hocko
2021-02-18 16:19 ` Minchan Kim
2021-02-18 16:26 ` David Hildenbrand
2021-02-18 16:47 ` Minchan Kim
2021-02-18 16:53 ` David Hildenbrand
2021-02-19 9:28 ` Michal Hocko
2021-02-19 9:30 ` David Hildenbrand
2021-02-19 10:02 ` Michal Hocko
2021-02-19 10:34 ` David Hildenbrand
[not found] ` <YD50pcPuwV456vwm@google.com>
2021-03-04 16:01 ` Minchan Kim
2021-03-04 16:10 ` David Hildenbrand
2021-03-04 16:23 ` Minchan Kim
2021-03-04 16:28 ` David Hildenbrand
2021-03-04 17:11 ` Minchan Kim
2021-03-04 17:23 ` David Hildenbrand
2021-03-04 18:11 ` Minchan Kim
2021-03-04 18:22 ` Minchan Kim
2021-03-08 12:49 ` Michal Hocko
2021-03-08 13:22 ` David Hildenbrand
2021-03-08 14:11 ` Michal Hocko
2021-03-08 14:13 ` David Hildenbrand
2021-03-08 15:42 ` Michal Hocko
2021-03-08 15:58 ` Minchan Kim
2021-03-08 16:21 ` Michal Hocko
2021-03-08 17:01 ` Minchan Kim
2021-03-08 20:27 ` Minchan Kim
2021-02-18 16:10 ` Minchan Kim
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