From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx162.postini.com [74.125.245.162]) by kanga.kvack.org (Postfix) with SMTP id 263056B0071 for ; Wed, 30 May 2012 11:14:09 -0400 (EDT) Message-ID: <4FC6393B.7090105@draigBrady.com> Date: Wed, 30 May 2012 16:14:03 +0100 From: =?ISO-8859-1?Q?P=E1draig_Brady?= MIME-Version: 1.0 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> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: 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 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, Padraig. -- 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