From: Michal Hocko <mhocko@kernel.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org
Subject: Re: [PATCH 04/20] arm: get rid of superfluous __GFP_REPEAT
Date: Thu, 28 Apr 2016 17:08:31 +0200 [thread overview]
Message-ID: <20160428150831.GK31489@dhcp22.suse.cz> (raw)
In-Reply-To: <20160428145545.GN19428@n2100.arm.linux.org.uk>
On Thu 28-04-16 15:55:45, Russell King - ARM Linux wrote:
> On Thu, Apr 28, 2016 at 03:23:50PM +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'm unconvinced. Back in 2013, I was seeing a lot of failures, so:
>
> 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>
>
> Maybe something has changed again in the MM layer which makes this flag
> unnecessary again, and it was a temporary blip around that time, I don't
> know.
PAGE_ALLOC_COSTLY_ORDER is defined to order 3 since 2007 and even before
the code was doing
- if ((order <= 3) || (gfp_mask & __GFP_REPEAT))
+ if ((order <= PAGE_ALLOC_COSTLY_ORDER) ||
+ (gfp_mask & __GFP_REPEAT))
do_retry = 1;
So an order-2 allocation which is the case for this particular code now
will trigger the OOM killer and fail only when the current task is
killed by the OOM killer. Other than that order-2 is basically
GFP_NOFAIL. Have a look at __alloc_pages_slowpath() for more details.
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-04-28 15:08 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-28 13:23 [PATCH 0/19] get rid of superfluous __GFP_REPEAT Michal Hocko
2016-04-28 13:23 ` [PATCH 01/20] tree wide: get rid of __GFP_REPEAT for order-0 allocations part I Michal Hocko
2016-04-28 13:23 ` [PATCH 02/20] x86: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-04-28 13:23 ` [PATCH 03/20] x86/efi: " Michal Hocko
2016-04-28 13:23 ` [PATCH 04/20] arm: " Michal Hocko
2016-04-28 14:55 ` Russell King - ARM Linux
2016-04-28 15:08 ` Michal Hocko [this message]
2016-04-29 9:41 ` Michal Hocko
2016-04-28 13:23 ` [PATCH 05/20] arm64: " Michal Hocko
2016-04-28 13:23 ` [PATCH 06/20] arc: " Michal Hocko
2016-04-28 13:23 ` [PATCH 07/20] mips: " Michal Hocko
2016-04-28 13:23 ` [PATCH 08/20] nios2: " Michal Hocko
2016-04-28 13:23 ` [PATCH 09/20] parisc: " Michal Hocko
2016-04-28 13:23 ` [PATCH 10/20] score: " Michal Hocko
2016-04-28 13:23 ` [PATCH 11/20] powerpc: " Michal Hocko
2016-04-28 13:23 ` [PATCH 12/20] sparc: " Michal Hocko
2016-04-28 13:23 ` [PATCH 13/20] s390: " Michal Hocko
2016-04-28 13:24 ` [PATCH 14/20] sh: " Michal Hocko
2016-04-28 13:24 ` [PATCH 15/20] tile: " Michal Hocko
2016-04-28 16:21 ` Chris Metcalf
2016-04-28 13:24 ` [PATCH 16/20] unicore32: " Michal Hocko
2016-04-28 13:24 ` [PATCH 17/20] dm: get rid of superfluous gfp flags Michal Hocko
2016-04-29 18:54 ` Mike Snitzer
2016-05-02 7:31 ` Michal Hocko
2016-04-28 13:24 ` [PATCH 18/20] dm: clean up GFP_NIO usage Michal Hocko
2016-04-28 14:20 ` Mikulas Patocka
2016-04-28 14:41 ` Michal Hocko
2016-04-28 13:24 ` [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback Michal Hocko
2016-04-28 14:51 ` [PATCH] " Michal Hocko
2016-04-28 15:04 ` Mikulas Patocka
2016-04-28 15:28 ` Michal Hocko
2016-04-28 15:40 ` Mikulas Patocka
2016-04-28 16:59 ` Michal Hocko
2016-04-28 15:37 ` [PATCH 19/20] " Mike Snitzer
2016-04-28 16:00 ` Michal Hocko
2016-04-28 13:24 ` [PATCH 20/20] jbd2: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-05-12 16:53 ` [PATCH 0/19] " Michal Hocko
2016-05-12 20:13 ` Andrew Morton
2016-05-13 6:58 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160428150831.GK31489@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@arm.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).