Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753996Ab2E3PON (ORCPT ); Wed, 30 May 2012 11:14:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60083 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753476Ab2E3POL (ORCPT ); Wed, 30 May 2012 11:14:11 -0400 Message-ID: <4FC6393B.7090105@draigBrady.com> Date: Wed, 30 May 2012 16:14:03 +0100 From: =?ISO-8859-1?Q?P=E1draig_Brady?= User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0) Gecko/20110816 Thunderbird/6.0 MIME-Version: 1.0 To: Cong Wang CC: linux-kernel@vger.kernel.org, Andrew Morton , Cong Wang , Alexander Viro , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC Patch] fs: implement per-file drop caches References: <1338385120-14519-1-git-send-email-amwang@redhat.com> In-Reply-To: <1338385120-14519-1-git-send-email-amwang@redhat.com> X-Enigmail-Version: 1.3.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1289 Lines: 36 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? This functionality was added to GNU dd (8.11) a year ago: http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=5f31155 Here are the examples from that patch: # Advise to drop cache for whole file dd if=ifile iflag=nocache count=0 # Ensure drop cache for the whole file dd of=ofile oflag=nocache conv=notrunc,fdatasync count=0 # Drop cache for part of file dd if=ifile iflag=nocache skip=10 count=10 of=/dev/null # Stream data using just the read-ahead cache dd if=ifile of=ofile iflag=nocache oflag=nocache cheers, P?draig. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/