Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932453AbWEZLzw (ORCPT ); Fri, 26 May 2006 07:55:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932460AbWEZLxg (ORCPT ); Fri, 26 May 2006 07:53:36 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:11483 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S932450AbWEZLxN (ORCPT ); Fri, 26 May 2006 07:53:13 -0400 Message-ID: <348644390.06434@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20060526115315.823465555@localhost.localdomain> References: <20060526113906.084341801@localhost.localdomain> Date: Fri, 26 May 2006 19:39:34 +0800 From: Wu Fengguang To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Wu Fengguang Subject: [PATCH 28/33] readahead: loop case Content-Disposition: inline; filename=readahead-loop-case.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1138 Lines: 36 Disable look-ahead for loop file. Loopback files normally contain filesystems, in which case there are already proper look-aheads in the upper layer, more look-aheads on the loopback file only ruins the read-ahead hit rate. Signed-off-by: Wu Fengguang --- I'd like to thank Tero Grundstr?m for uncovering the loopback problem. drivers/block/loop.c | 6 ++++++ 1 files changed, 6 insertions(+) --- linux-2.6.17-rc4-mm3.orig/drivers/block/loop.c +++ linux-2.6.17-rc4-mm3/drivers/block/loop.c @@ -779,6 +779,12 @@ static int loop_set_fd(struct loop_devic mapping = file->f_mapping; inode = mapping->host; + /* + * The upper layer should already do proper look-ahead, + * one more look-ahead here only ruins the cache hit rate. + */ + file->f_ra.flags |= RA_FLAG_NO_LOOKAHEAD; + if (!(file->f_mode & FMODE_WRITE)) lo_flags |= LO_FLAGS_READ_ONLY; -- - 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/