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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?

  parent reply	other threads:[~2016-07-20 20:59 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1464599699-30131-1-git-send-email-mhocko@kernel.org>
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   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 02/17] x86: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 03/17] x86/efi: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 04/17] arm: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-06-01 16:24   ` Russell King - ARM Linux
2016-06-01 16:24     ` Russell King - ARM Linux
2016-06-02  6:32     ` Michal Hocko
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   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 06/17] arc: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 07/17] mips: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 08/17] nios2: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 09/17] parisc: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 10/17] score: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 11/17] powerpc: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 12/17] sparc: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30 18:23   ` David Miller
2016-05-30 18:23     ` David Miller
2016-05-30  9:14 ` [PATCH 13/17] s390: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 14/17] sh: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 15/17] tile: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko
2016-05-30  9:14 ` [PATCH 16/17] unicore32: " Michal Hocko
2016-05-30  9:14   ` Michal Hocko

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