From: Michal Hocko <mhocko@kernel.org>
To: <linux-mm@kvack.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Chen Liqin <liqin.linux@gmail.com>,
Chris Metcalf <cmetcalf@mellanox.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
"David S. Miller" <davem@davemloft.net>,
Guan Xuetao <gxt@mprc.pku.edu.cn>, Helge Deller <deller@gmx.de>,
Herbert Xu <herbert@gondor.apana.org.au>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
John Crispin <blogic@openwrt.org>,
Lennox Wu <lennox.wu@gmail.com>, Ley Foon Tan <lftan@altera.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Michal Hocko <mhocko@suse.com>,
Mikulas Patocka <mpatocka@redhat.com>,
Rich Felker <dalias@libc.org>,
Russell King <linux@arm.linux.org.uk>,
Shaohua Li <shli@kernel.org>, "Theodore Ts'o" <tytso@mit.edu>,
Thomas Gleixner <tglx@linutronix.de>,
Vineet Gupta <vgupta@synopsys.com>,
Will Deacon <will.deacon@arm.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>
Subject: [PATCH 0/19] get rid of superfluous __GFP_REPORT
Date: Mon, 11 Apr 2016 13:07:53 +0200 [thread overview]
Message-ID: <1460372892-8157-1-git-send-email-mhocko@kernel.org> (raw)
Hi,
this is the second version of the patchset previously sent [1]
while working on something unrelated I've checked the current usage
of __GFP_REPEAT in the tree. It seems that a majority of the usage is
and always has been bogus because __GFP_REPEAT has always been about
costly high order allocations while we are using it for order-0 or very
small orders very often. It seems that a big pile of them is just a
copy&paste when a code has been adopted from one arch to another.
I think it makes some sense to get rid of them because they are just
making the semantic more unclear. Please note that GFP_REPEAT is
documented as
* __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt
* _might_ fail. This depends upon the particular VM implementation.
while !costly requests have basically nofail semantic. So one could
reasonably expect that order-0 request with __GFP_REPEAT will not loop
for ever. This is not implemented right now though.
I would like to move on with __GFP_REPEAT and define a better
semantic for it. One thought was to rename it to __GFP_BEST_EFFORT
which would behave consistently for all orders and guarantee that the
allocation would try as long as it seem feasible or fail eventually.
!costly request would then finally get a request context which neiter
fails too early (GFP_NORETRY) nor endlessly loops in the allocator for
ever (default behavior). Costly high order requests would keep the
current semantic.
$ git grep __GFP_REPEAT next/master | wc -l
111
$ git grep __GFP_REPEAT | wc -l
35
So we are down to the third after this patch series. The remaining places
really seem to be relying on __GFP_REPEAT due to large allocation requests.
This still needs some double checking which I will do later after all the
simple ones are sorted out.
I am touching a lot of arch specific code here and I hope I got it right
but as a matter of fact I even didn't compile test for some archs as I
do not have cross compiler for them. Patches should be quite trivial to
review for stupid compile mistakes though. The tricky parts are usually
hidden by macro definitions and thats where I would appreciate help from
arch maintainers.
I am also interested whether this makes sense in general.
[1] http://lkml.kernel.org/r/1446740160-29094-1-git-send-email-mhocko@kernel.org
next reply other threads:[~2016-04-11 11:08 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-11 11:07 Michal Hocko [this message]
2016-04-11 11:07 ` [PATCH 01/19] tree wide: get rid of __GFP_REPEAT for order-0 allocations part I Michal Hocko
2016-04-14 19:56 ` David Rientjes
2016-04-15 7:44 ` Michal Hocko
2016-04-11 11:07 ` [PATCH 02/19] x86: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-04-11 11:07 ` [PATCH 03/19] x86/efi: " Michal Hocko
2016-04-12 15:53 ` Matt Fleming
2016-04-11 11:07 ` [PATCH 04/19] arm: " Michal Hocko
2016-04-11 11:07 ` [PATCH 05/19] arm64: " Michal Hocko
2016-04-11 15:49 ` Will Deacon
2016-04-11 11:07 ` [PATCH 06/19] arc: " Michal Hocko
2016-04-11 14:23 ` Vineet Gupta
2016-04-11 11:08 ` [PATCH 07/19] mips: " Michal Hocko
2016-04-11 11:08 ` [PATCH 08/19] nios2: " Michal Hocko
2016-04-11 11:08 ` [PATCH 09/19] parisc: " Michal Hocko
2016-04-11 11:08 ` [PATCH 10/19] score: " Michal Hocko
2016-04-11 11:08 ` [PATCH 11/19] powerpc: " Michal Hocko
2016-04-11 11:08 ` [PATCH 12/19] sparc: " Michal Hocko
2016-04-11 11:08 ` [PATCH 13/19] s390: " Michal Hocko
2016-04-11 11:28 ` Cornelia Huck
2016-04-11 12:47 ` Heiko Carstens
2016-04-11 11:08 ` [PATCH 14/19] sh: " Michal Hocko
2016-04-11 11:08 ` [PATCH 15/19] tile: " Michal Hocko
2016-04-11 11:08 ` [PATCH 16/19] unicore32: " Michal Hocko
2016-04-11 11:08 ` [PATCH 17/19] dm: get rid of superfluous gfp flags Michal Hocko
2016-04-15 12:29 ` Mikulas Patocka
2016-04-15 13:08 ` Michal Hocko
2016-04-15 18:41 ` Mikulas Patocka
2016-04-16 20:31 ` Michal Hocko
2016-04-22 12:47 ` Michal Hocko
2016-04-26 17:20 ` Mikulas Patocka
2016-04-27 8:35 ` Michal Hocko
2016-04-11 11:08 ` [PATCH 18/19] crypto: get rid of superfluous __GFP_REPEAT Michal Hocko
2016-04-14 6:27 ` Herbert Xu
2016-04-14 7:02 ` Michal Hocko
2016-04-14 8:16 ` Herbert Xu
2016-04-14 8:51 ` [PATCH resend] " Michal Hocko
2016-04-15 14:37 ` Herbert Xu
2016-04-11 11:08 ` [PATCH 19/19] jbd2: " Michal Hocko
2016-04-13 11:21 ` CC in git cover letter vs patches (was Re: [PATCH 0/19] get rid of superfluous __GFP_REPORT) Vineet Gupta
2016-04-13 13:33 ` Michal Hocko
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