From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938114AbZDJNT5 (ORCPT ); Fri, 10 Apr 2009 09:19:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937295AbZDJNTM (ORCPT ); Fri, 10 Apr 2009 09:19:12 -0400 Received: from mga03.intel.com ([143.182.124.21]:31389 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937326AbZDJNTK (ORCPT ); Fri, 10 Apr 2009 09:19:10 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.40,166,1239001200"; d="scan'208";a="130105413" Message-Id: <20090410131358.930803287@intel.com> References: <20090410131247.764370473@intel.com> User-Agent: quilt/0.46-1 Date: Fri, 10 Apr 2009 21:12:49 +0800 From: Wu Fengguang To: Andrew Morton Cc: Vladislav Bolkhovitin , Wu Fengguang Cc: LKML Subject: [PATCH 2/3] readahead: move the random read case to bottom Content-Disposition: inline; filename=readahead-reorder-cases.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Split all readahead cases, and move the random one to bottom. No behavior changes. This is to prepare for the introduction of context readahead, and make it easy for inserting accounting/tracing points for each case. Signed-off-by: Wu Fengguang --- mm/readahead.c | 46 +++++++++++++++++++++++++--------------------- 1 file changed, 25 insertions(+), 21 deletions(-) --- mm.orig/mm/readahead.c +++ mm/mm/readahead.c @@ -339,33 +339,25 @@ ondemand_readahead(struct address_space unsigned long req_size) { unsigned long max = max_sane_readahead(ra->ra_pages); - pgoff_t prev_offset; - int sequential; + + /* + * start of file + */ + if (!offset) + goto initial_readahead; /* * It's the expected callback offset, assume sequential access. * Ramp up sizes, and push forward the readahead window. */ - if (offset && (offset == (ra->start + ra->size - ra->async_size) || - offset == (ra->start + ra->size))) { + if ((offset == (ra->start + ra->size - ra->async_size) || + offset == (ra->start + ra->size))) { ra->start += ra->size; ra->size = get_next_ra_size(ra, max); ra->async_size = ra->size; goto readit; } - prev_offset = ra->prev_pos >> PAGE_CACHE_SHIFT; - sequential = offset - prev_offset <= 1UL || req_size > max; - - /* - * Standalone, small read. - * Read as is, and do not pollute the readahead state. - */ - if (!hit_readahead_marker && !sequential) { - return __do_page_cache_readahead(mapping, filp, - offset, req_size, 0); - } - /* * Hit a marked page without valid readahead state. * E.g. interleaved reads. @@ -391,12 +383,24 @@ ondemand_readahead(struct address_space } /* - * It may be one of - * - first read on start of file - * - sequential cache miss - * - oversize random read - * Start readahead for it. + * oversize read */ + if (req_size > max) + goto initial_readahead; + + /* + * sequential cache miss + */ + if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL) + goto initial_readahead; + + /* + * standalone, small random read + * Read as is, and do not pollute the readahead state. + */ + return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); + +initial_readahead: ra->start = offset; ra->size = get_init_ra_size(req_size, max); ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; --