From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH 04/17] arm: get rid of superfluous __GFP_REPEAT Date: Wed, 1 Jun 2016 17:24:24 +0100 Message-ID: <20160601162424.GD19428@n2100.arm.linux.org.uk> References: <1464599699-30131-1-git-send-email-mhocko@kernel.org> <1464599699-30131-5-git-send-email-mhocko@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1464599699-30131-5-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, LKML , Michal Hocko , linux-arch@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote: > From: Michal Hocko > > __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 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 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? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- 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: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pandora.armlinux.org.uk ([78.32.30.218]:47486 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751808AbcFAQYg (ORCPT ); Wed, 1 Jun 2016 12:24:36 -0400 Date: Wed, 1 Jun 2016 17:24:24 +0100 From: Russell King - ARM Linux Subject: Re: [PATCH 04/17] arm: get rid of superfluous __GFP_REPEAT Message-ID: <20160601162424.GD19428@n2100.arm.linux.org.uk> References: <1464599699-30131-1-git-send-email-mhocko@kernel.org> <1464599699-30131-5-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464599699-30131-5-git-send-email-mhocko@kernel.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, LKML , Michal Hocko , linux-arch@vger.kernel.org Message-ID: <20160601162424.jjP6mJMljSd21RjsDHjNYyGiHzY8EAGAqiImYq18kT8@z> On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote: > From: Michal Hocko > > __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 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 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? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.