From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [RFC Patch] fs: implement per-file drop caches Date: Thu, 31 May 2012 02:30:22 -0400 Message-ID: <4FC70FFE.50809@gmail.com> References: <1338385120-14519-1-git-send-email-amwang@redhat.com> <4FC6393B.7090105@draigBrady.com> <1338445233.19369.21.camel@cr0> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Cc: =?UTF-8?B?UMOhZHJhaWcgQnJhZHk=?= , linux-kernel@vger.kernel.org, Andrew Morton , Cong Wang , Alexander Viro , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, kosaki.motohiro@gmail.com To: Cong Wang Return-path: In-Reply-To: <1338445233.19369.21.camel@cr0> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org (5/31/12 2:20 AM), Cong Wang wrote: > On Wed, 2012-05-30 at 16:14 +0100, P=C3=A1draig Brady wrote: >> On 05/30/2012 02:38 PM, Cong Wang wrote: >>> This is a draft patch of implementing per-file drop caches. >>> >>> It introduces a new fcntl command F_DROP_CACHES to drop >>> file caches of a specific file. The reason is that currently >>> we only have a system-wide drop caches interface, it could >>> cause system-wide performance down if we drop all page caches >>> when we actually want to drop the caches of some huge file. >> >> This is useful functionality. >> Though isn't it already provided with POSIX_FADV_DONTNEED? > > Thanks for teaching this! > > However, from the source code of madvise_dontneed() it looks like it is > using a totally different way to drop page caches, that is to invalidat= e > the page mapping, and trigger a re-mapping of the file pages after a > page fault. So, yeah, this could probably drop the page caches too (I a= m > not so sure, haven't checked the code in details), but with my patch, i= t > flushes the page caches directly, what's more, it can also prune > dcache/icache of the file. madvise should work. I don't think we need duplicate interface. Moreomove= r madvise(2) is cleaner than fcntl(2). -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter= .ca/ Don't email: email@kvack.org