From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?P=E1draig_Brady?= Subject: Re: [RFC Patch] fs: implement per-file drop caches Date: Wed, 30 May 2012 16:14:03 +0100 Message-ID: <4FC6393B.7090105@draigBrady.com> References: <1338385120-14519-1-git-send-email-amwang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: linux-kernel@vger.kernel.org, Andrew Morton , Cong Wang , Alexander Viro , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org To: Cong Wang Return-path: In-Reply-To: <1338385120-14519-1-git-send-email-amwang@redhat.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On 05/30/2012 02:38 PM, Cong Wang wrote: > This is a draft patch of implementing per-file drop caches. >=20 > 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=3Dcoreutils.git;a=3Dcommitdiff;h=3D5f3115= 5 Here are the examples from that patch: # Advise to drop cache for whole file dd if=3Difile iflag=3Dnocache count=3D0 # Ensure drop cache for the whole file dd of=3Dofile oflag=3Dnocache conv=3Dnotrunc,fdatasync count=3D0 # Drop cache for part of file dd if=3Difile iflag=3Dnocache skip=3D10 count=3D10 of=3D/dev/null # Stream data using just the read-ahead cache dd if=3Difile of=3Dofile iflag=3Dnocache oflag=3Dnocache cheers, P=E1draig. -- 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