From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@suse.de>, NeilBrown <neilb@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 4/6] mm: kvmalloc support __GFP_RETRY_MAYFAIL for all sizes
Date: Mon, 26 Jun 2017 14:18:37 +0200 [thread overview]
Message-ID: <20170626121836.GL11534@dhcp22.suse.cz> (raw)
In-Reply-To: <80500165-94c2-2d5c-ff7a-6310916da288@suse.cz>
On Mon 26-06-17 14:00:27, Vlastimil Babka wrote:
> On 06/23/2017 10:53 AM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> > Now that __GFP_RETRY_MAYFAIL has a reasonable semantic regardless of the
> > request size we can drop the hackish implementation for !costly orders.
> > __GFP_RETRY_MAYFAIL retries as long as the reclaim makes a forward
> > progress and backs of when we are out of memory for the requested size.
> > Therefore we do not need to enforce__GFP_NORETRY for !costly orders just
> > to silent the oom killer anymore.
> >
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
>
> The flag is now supported, but not for the embedded page table
> allocations, so OOM is still theoretically possible, right?
> That should be rare, though. Worth mentioning anywhere?
Yes that is true. Not sure I would make it more complicated than
necessary. I can add a note in there if you insist but to me it sounds
like something that will only confuse people.
> Other than that.
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
Thanks!
> > ---
> > mm/util.c | 14 ++++----------
> > 1 file changed, 4 insertions(+), 10 deletions(-)
> >
> > diff --git a/mm/util.c b/mm/util.c
> > index 6520f2d4a226..ee250e2cde34 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -339,9 +339,9 @@ EXPORT_SYMBOL(vm_mmap);
> > * Uses kmalloc to get the memory but if the allocation fails then falls back
> > * to the vmalloc allocator. Use kvfree for freeing the memory.
> > *
> > - * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. __GFP_RETRY_MAYFAIL
> > - * is supported only for large (>32kB) allocations, and it should be used only if
> > - * kmalloc is preferable to the vmalloc fallback, due to visible performance drawbacks.
> > + * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
> > + * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
> > + * preferable to the vmalloc fallback, due to visible performance drawbacks.
> > *
> > * Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
> > */
> > @@ -366,13 +366,7 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
> > if (size > PAGE_SIZE) {
> > kmalloc_flags |= __GFP_NOWARN;
> >
> > - /*
> > - * We have to override __GFP_RETRY_MAYFAIL by __GFP_NORETRY for !costly
> > - * requests because there is no other way to tell the allocator
> > - * that we want to fail rather than retry endlessly.
> > - */
> > - if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL) ||
> > - (size <= PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
> > + if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
> > kmalloc_flags |= __GFP_NORETRY;
> > }
> >
> >
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-06-26 12:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-23 8:53 [PATCH 0/6] mm: give __GFP_REPEAT a better semantic Michal Hocko
2017-06-23 8:53 ` [PATCH 1/6] MIPS: do not use __GFP_REPEAT for order-0 request Michal Hocko
2017-06-23 10:27 ` Ralf Baechle
2017-06-26 9:36 ` Vlastimil Babka
2017-06-23 8:53 ` [PATCH 2/6] mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful semantic Michal Hocko
2017-06-26 11:45 ` Vlastimil Babka
2017-06-26 12:14 ` Michal Hocko
2017-06-26 12:17 ` Vlastimil Babka
2017-06-26 12:38 ` Michal Hocko
2017-06-26 12:42 ` Michal Hocko
2017-06-26 11:53 ` Vlastimil Babka
2017-06-23 8:53 ` [PATCH 3/6] xfs: map KM_MAYFAIL to __GFP_RETRY_MAYFAIL Michal Hocko
2017-06-27 8:49 ` Michal Hocko
2017-06-27 13:47 ` Christoph Hellwig
2017-06-27 14:06 ` Michal Hocko
2017-06-28 4:12 ` Darrick J. Wong
2017-06-23 8:53 ` [PATCH 4/6] mm: kvmalloc support __GFP_RETRY_MAYFAIL for all sizes Michal Hocko
2017-06-26 12:00 ` Vlastimil Babka
2017-06-26 12:18 ` Michal Hocko [this message]
2017-06-23 8:53 ` [PATCH 5/6] drm/i915: use __GFP_RETRY_MAYFAIL Michal Hocko
2017-06-23 8:53 ` [PATCH 6/6] mm, migration: do not trigger OOM killer when migrating memory Michal Hocko
2017-06-23 20:43 ` Andrew Morton
2017-06-26 5:28 ` Michal Hocko
2017-06-26 12:13 ` Vlastimil Babka
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