From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754439AbcE3JPK (ORCPT ); Mon, 30 May 2016 05:15:10 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33484 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752561AbcE3JPI (ORCPT ); Mon, 30 May 2016 05:15:08 -0400 From: Michal Hocko To: Andrew Morton Cc: , LKML , Andy Lutomirski , Benjamin Herrenschmidt , Catalin Marinas , Chen Liqin , Chris Metcalf , "David S. Miller" , Guan Xuetao , Heiko Carstens , Helge Deller , "H. Peter Anvin" , Ingo Molnar , "James E.J. Bottomley" , Jan Kara , John Crispin , Lennox Wu , Ley Foon Tan , Martin Schwidefsky , Matt Fleming , Michal Hocko , Rich Felker , Russell King , "Theodore Ts'o" , Thomas Gleixner , Vineet Gupta , Will Deacon , Yoshinori Sato Subject: [PATCH 0/19] get rid of superfluous __GFP_REPEAT Date: Mon, 30 May 2016 11:14:42 +0200 Message-Id: <1464599699-30131-1-git-send-email-mhocko@kernel.org> X-Mailer: git-send-email 2.8.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, this is the thrid version of the patchset previously sent [1]. I have basically only rebased it on top of 4.7-rc1 tree and dropped "dm: get rid of superfluous gfp flags" which went through dm tree. I am sending it now because it is tree wide and chances for conflicts are reduced considerably when we want to target rc2. I plan to send the next step and rename the flag and move to a better semantic later during this release cycle so we will have a new semantic ready for 4.8 merge window hopefully. Motivation: 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. $ git grep __GFP_REPEAT origin/master | wc -l 111 $ git grep __GFP_REPEAT | wc -l 36 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. [1] http://lkml.kernel.org/r/1461849846-27209-1-git-send-email-mhocko@kernel.org