Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751376AbWCSCmx (ORCPT ); Sat, 18 Mar 2006 21:42:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751291AbWCSCls (ORCPT ); Sat, 18 Mar 2006 21:41:48 -0500 Received: from ns.ustc.edu.cn ([202.38.64.1]:43202 "EHLO mx1.ustc.edu.cn") by vger.kernel.org with ESMTP id S1751289AbWCSCef (ORCPT ); Sat, 18 Mar 2006 21:34:35 -0500 Message-Id: <20060319023458.060047000@localhost.localdomain> References: <20060319023413.305977000@localhost.localdomain> Date: Sun, 19 Mar 2006 10:34:32 +0800 From: Wu Fengguang To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Wu Fengguang Subject: [PATCH 19/23] 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-2.6.16-rc6-mm2.orig/drivers/block/loop.c +++ linux-2.6.16-rc6-mm2/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/