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Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in blkcg

From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in blkcg
Date 2016-11-22 23:20 +0100
Message-ID <sGrzX-4Ma-9@gated-at.bofh.it> (permalink)
References (1 earlier) <sG4N4-6GD-11@gated-at.bofh.it> <sG56q-77c-7@gated-at.bofh.it> <sG5SN-7Cz-15@gated-at.bofh.it> <sGluy-yw-13@gated-at.bofh.it> <sGmJY-1DN-35@gated-at.bofh.it>
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On Tue, Nov 22, 2016 at 8:48 AM, Tejun Heo <tj@kernel.org> wrote:
>
> Hello,
>
> On Tue, Nov 22, 2016 at 04:47:49PM +0100, Vlastimil Babka wrote:
> > Thanks. Makes me wonder whether we should e.g. add __GFP_NOWARN to
> > GFP_NOWAIT globally at some point.
>
> Yeah, that makes sense.  The caller is explicitly saying that it's
> okay to fail the allocation.

I'm not so convinced about the "atomic automatically means you shouldn't warn".

You'd certainly _hope_ that atomic allocations either have fallbacks
or are harmless if they fail, but I'd still rather see that
__GFP_NOWARN just to make that very much explicit.

Because as it is, atomic allocations certainly get to dig deeper into
our memory reserves, but they most definitely can fail, and I
definitely see how some code has no fallback because it thinks that
the deeper reserves mean that it will succeed.

             Linus

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Thread

Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Vlastimil Babka <vbabka@suse.cz> - 2016-11-21 23:00 +0100
  Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of RAM that should be free Marc MERLIN <marc@merlins.org> - 2016-11-21 23:20 +0100
    [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in  blkcg Tejun Heo <tj@kernel.org> - 2016-11-22 00:10 +0100
      Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations  in blkcg Vlastimil Babka <vbabka@suse.cz> - 2016-11-22 16:50 +0100
        Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort  allocations in blkcg Tejun Heo <tj@kernel.org> - 2016-11-22 18:10 +0100
          Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations  in blkcg Linus Torvalds <torvalds@linux-foundation.org> - 2016-11-22 23:20 +0100
            Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations  in blkcg Vlastimil Babka <vbabka@suse.cz> - 2016-11-23 10:00 +0100
      Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations  in blkcg Jens Axboe <axboe@kernel.dk> - 2016-11-22 17:10 +0100
    Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Marc MERLIN <marc@merlins.org> - 2016-11-22 17:10 +0100
      Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Vlastimil Babka <vbabka@suse.cz> - 2016-11-22 17:20 +0100
        Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Michal Hocko <mhocko@kernel.org> - 2016-11-22 17:30 +0100
          Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Marc MERLIN <marc@merlins.org> - 2016-11-22 17:50 +0100
        Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-22 17:40 +0100
        Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Linus Torvalds <torvalds@linux-foundation.org> - 2016-11-22 20:40 +0100
          Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Michal Hocko <mhocko@kernel.org> - 2016-11-23 07:40 +0100
            Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of RAM that should be free "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2016-11-23 08:00 +0100
              Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Michal Hocko <mhocko@kernel.org> - 2016-11-23 08:10 +0100
            Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Vlastimil Babka <vbabka@suse.cz> - 2016-11-23 11:20 +0100
        Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of  RAM that should be free Simon Kirby <sim@hostway.ca> - 2016-11-22 23:10 +0100

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