From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH v2] mm: hugetlb: add arch hook for clearing page flags before entering pool Date: Fri, 24 Aug 2012 15:01:54 -0700 Message-ID: <20120824150154.fc16a78e.akpm@linux-foundation.org> References: <1345739833-25008-1-git-send-email-will.deacon@arm.com> <20120823171156.GE19968@dhcp22.suse.cz> <20120823173602.GA3117@mudshark.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120823173602.GA3117@mudshark.cambridge.arm.com> Sender: owner-linux-mm@kvack.org To: Will Deacon Cc: Michal Hocko , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" List-Id: linux-arch.vger.kernel.org On Thu, 23 Aug 2012 18:36:02 +0100 Will Deacon wrote: > On Thu, Aug 23, 2012 at 06:11:56PM +0100, Michal Hocko wrote: > > On Thu 23-08-12 17:37:13, Will Deacon wrote: > > > The core page allocator ensures that page flags are zeroed when freeing > > > pages via free_pages_check. A number of architectures (ARM, PPC, MIPS) > > > rely on this property to treat new pages as dirty with respect to the > > > data cache and perform the appropriate flushing before mapping the pages > > > into userspace. > > > > > > This can lead to cache synchronisation problems when using hugepages, > > > since the allocator keeps its own pool of pages above the usual page > > > allocator and does not reset the page flags when freeing a page into > > > the pool. > > > > > > This patch adds a new architecture hook, arch_clear_hugepage_flags, so > > > that architectures which rely on the page flags being in a particular > > > state for fresh allocations can adjust the flags accordingly when a > > > page is freed into the pool. You could have used __weak here quite neatly, but whatever. > Next step: start posting the ARM code! I suggest you keep this patch in whichever tree holds that arm code. If I see this patch turn up in linux-next then I'll just drop my copy, expecting that this patch will be merged alongside the ARM changes. -- 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 mail.linuxfoundation.org ([140.211.169.12]:54809 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932349Ab2HXWBz (ORCPT ); Fri, 24 Aug 2012 18:01:55 -0400 Date: Fri, 24 Aug 2012 15:01:54 -0700 From: Andrew Morton Subject: Re: [PATCH v2] mm: hugetlb: add arch hook for clearing page flags before entering pool Message-ID: <20120824150154.fc16a78e.akpm@linux-foundation.org> In-Reply-To: <20120823173602.GA3117@mudshark.cambridge.arm.com> References: <1345739833-25008-1-git-send-email-will.deacon@arm.com> <20120823171156.GE19968@dhcp22.suse.cz> <20120823173602.GA3117@mudshark.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Will Deacon Cc: Michal Hocko , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" Message-ID: <20120824220154.z1RsLvNfPoyF7_F04jBvqkNmrYe8sdmVfADXDL4i14o@z> On Thu, 23 Aug 2012 18:36:02 +0100 Will Deacon wrote: > On Thu, Aug 23, 2012 at 06:11:56PM +0100, Michal Hocko wrote: > > On Thu 23-08-12 17:37:13, Will Deacon wrote: > > > The core page allocator ensures that page flags are zeroed when freeing > > > pages via free_pages_check. A number of architectures (ARM, PPC, MIPS) > > > rely on this property to treat new pages as dirty with respect to the > > > data cache and perform the appropriate flushing before mapping the pages > > > into userspace. > > > > > > This can lead to cache synchronisation problems when using hugepages, > > > since the allocator keeps its own pool of pages above the usual page > > > allocator and does not reset the page flags when freeing a page into > > > the pool. > > > > > > This patch adds a new architecture hook, arch_clear_hugepage_flags, so > > > that architectures which rely on the page flags being in a particular > > > state for fresh allocations can adjust the flags accordingly when a > > > page is freed into the pool. You could have used __weak here quite neatly, but whatever. > Next step: start posting the ARM code! I suggest you keep this patch in whichever tree holds that arm code. If I see this patch turn up in linux-next then I'll just drop my copy, expecting that this patch will be merged alongside the ARM changes.