From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, bugzilla-daemon@bugzilla.kernel.org,
john@calva.com, Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [Bug 107111] New: page allocation failure but there seem to be free pages
Date: Wed, 4 Nov 2015 11:20:23 +0100 [thread overview]
Message-ID: <20151104102023.GF29607@dhcp22.suse.cz> (raw)
In-Reply-To: <20151103141603.261893b44e0cd6e704921fb6@linux-foundation.org>
On Tue 03-11-15 14:16:03, Andrew Morton wrote:
[...]
> > [1188431.177410] apache2: page allocation failure: order:1, mode:0x204020
>
> An order-1 page, __GFP_COMP|__GFP_HIGH. ie: GFP_ATOMIC.
__GFP_HIGH doesn't really work well on a small zone like DMA I am
afraid.
[...]
> > [1188431.177521] Node 0 DMA free:7968kB min:40kB low:48kB high:60kB
[...]
> > [1188431.177527] lowmem_reserve[]: 0 1988 1988 1988
[...]
> > [1188431.177555] Node 0 DMA: 44*4kB (UE) 94*8kB (UEM) 76*16kB (UE) 42*32kB
> > (UEM) 22*64kB (UEM) 6*128kB (UE) 3*256kB (UE) 1*512kB (E) 1*1024kB (U) 0*2048kB
> > 0*4096kB = 7968kB
>
> The DMA zone has lots and lots of higher-order pages available which
> could satisfy this allocation.
min = 10 - 10/2 = 5 # __GFP_HIGH
min = 5 - 5/4 = 4 # ALLOC_HARDER
free_pages = 1992 - ((1<<1) - 1) = 1991
free_cma = 0
1991 <= 4 + 1988
So we do not pass lowmem reserves check here...
[...]
> The kernel could and should have satisfied this order-1 GFP_ATOMIC
> IRQ-context allocation from the DMA zone. But it did not do so. Bug.
I am not really sure this is a bug to be honest. It seems that we are
not coping with the non sleeping allocation pressure. I would suggest
increasing min_free_kbytes.
--
Michal Hocko
SUSE Labs
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prev parent reply other threads:[~2015-11-04 10:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-107111-27@https.bugzilla.kernel.org/>
2015-11-03 22:16 ` Andrew Morton
2015-11-04 10:10 ` John Hughes
2015-11-04 10:20 ` Michal Hocko [this message]
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