From: Andrew Morton <akpm@linux-foundation.org>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>,
linux-arch@vger.kernel.org
Subject: Re: [PATCH 04/17] arm: get rid of superfluous __GFP_REPEAT
Date: Wed, 20 Jul 2016 13:59:00 -0700 [thread overview]
Message-ID: <20160720135900.6735fc0db41807c2edf88594@linux-foundation.org> (raw)
In-Reply-To: <20160601162424.GD19428@n2100.arm.linux.org.uk>
On Wed, 1 Jun 2016 17:24:24 +0100 Russell King - ARM Linux <linux@armlinux.org.uk> wrote:
> On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> > __GFP_REPEAT has a rather weak semantic but since it has been introduced
> > around 2.6.12 it has been ignored for low order allocations.
> >
> > PGALLOC_GFP uses __GFP_REPEAT but none of the allocation which uses
> > this flag is for more than order-2. This means that this flag has never
> > been actually useful here because it has always been used only for
> > PAGE_ALLOC_COSTLY requests.
>
> I hear what you say, but...
>
> commit 8c65da6dc89ccb605d73773b1dd617e72982d971
> Author: Russell King <rmk+kernel@arm.linux.org.uk>
> Date: Sat Nov 30 12:52:31 2013 +0000
>
> ARM: pgd allocation: retry on failure
>
> Make pgd allocation retry on failure; we really need this to succeed
> otherwise fork() can trigger OOMs.
>
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
>
> and that's the change which introduced this, and it did solve a problem
> for me. So I'm not happy to give an ack for this change unless someone
> can tell me why adding __GFP_REPEAT back then had a beneficial effect.
> Maybe there was some other bug in the MM layer in 2013 which this change
> happened to solve?
I suspect that some other change has made arm's use of __GFP_REPEAT
unnecessary, because __GFP_REPEAT is now a no-op for order-0,1,2,3
allocations and none of the arm callsites which I can see are using
order-4 or higher.
So I think we should go ahead with this change. If that causes some
problem then we'll need to dig in and figure out why the impossible
just happened, OK?
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next prev parent reply other threads:[~2016-07-20 20:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 9:14 [PATCH 0/19] get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-30 9:14 ` [PATCH 01/17] tree wide: get rid of __GFP_REPEAT for order-0 allocations part I Michal Hocko
2016-05-30 9:14 ` [PATCH 02/17] x86: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-30 9:14 ` [PATCH 03/17] x86/efi: " Michal Hocko
2016-05-30 9:14 ` [PATCH 04/17] arm: " Michal Hocko
2016-06-01 16:24 ` Russell King - ARM Linux
2016-06-02 6:32 ` Michal Hocko
2016-07-20 20:59 ` Andrew Morton [this message]
2016-05-30 9:14 ` [PATCH 05/17] arm64: " Michal Hocko
2016-05-30 9:14 ` [PATCH 06/17] arc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 07/17] mips: " Michal Hocko
2016-05-30 9:14 ` [PATCH 08/17] nios2: " Michal Hocko
2016-05-30 9:14 ` [PATCH 09/17] parisc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 10/17] score: " Michal Hocko
2016-05-30 9:14 ` [PATCH 11/17] powerpc: " Michal Hocko
2016-05-30 9:14 ` [PATCH 12/17] sparc: " Michal Hocko
2016-05-30 18:23 ` David Miller
2016-05-30 9:14 ` [PATCH 13/17] s390: " Michal Hocko
2016-05-30 9:14 ` [PATCH 14/17] sh: " Michal Hocko
2016-05-30 9:14 ` [PATCH 15/17] tile: " Michal Hocko
2016-05-30 9:14 ` [PATCH 16/17] unicore32: " Michal Hocko
2016-05-30 9:14 ` [PATCH 17/17] jbd2: " Michal Hocko
2016-05-30 13:09 ` Jan Kara
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