Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932709AbWEXLW3 (ORCPT ); Wed, 24 May 2006 07:22:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932704AbWEXLTr (ORCPT ); Wed, 24 May 2006 07:19:47 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:17538 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S932688AbWEXLTM (ORCPT ); Wed, 24 May 2006 07:19:12 -0400 Message-ID: <348469549.07101@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20060524111911.032100160@localhost.localdomain> References: <20060524111246.420010595@localhost.localdomain> Date: Wed, 24 May 2006 19:13:14 +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/