From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757948Ab1D3Dbp (ORCPT ); Fri, 29 Apr 2011 23:31:45 -0400 Received: from mga02.intel.com ([134.134.136.20]:7788 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756849Ab1D3Dbn (ORCPT ); Fri, 29 Apr 2011 23:31:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,292,1301900400"; d="scan'208";a="740455729" Message-Id: <20110430033017.923224207@intel.com> User-Agent: quilt/0.48-1 Date: Sat, 30 Apr 2011 11:22:44 +0800 From: Wu Fengguang To: Andrew Morton To: Andi Kleen cc: Tim Chen , Wu Fengguang cc: Li Shaohua Cc: LKML cc: Linux Memory Management List Subject: [PATCH 1/3] readahead: return early when readahead is disabled References: <20110430032243.355805181@intel.com> Content-Disposition: inline; filename=readahead-early-abort-mmap-around.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reduce readahead overheads by returning early in do_sync_mmap_readahead(). tmpfs has ra_pages=0 and it can page fault really fast (not constraint by IO if not swapping). Tested-by: Tim Chen Reported-by: Andi Kleen Signed-off-by: Wu Fengguang --- mm/filemap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- linux-next.orig/mm/filemap.c 2011-04-23 08:56:59.000000000 +0800 +++ linux-next/mm/filemap.c 2011-04-23 09:01:44.000000000 +0800 @@ -1528,6 +1528,8 @@ static void do_sync_mmap_readahead(struc /* If we don't want any read-ahead, don't bother */ if (VM_RandomReadHint(vma)) return; + if (!ra->ra_pages) + return; if (VM_SequentialReadHint(vma) || offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { @@ -1550,12 +1552,10 @@ static void do_sync_mmap_readahead(struc * mmap read-around */ ra_pages = max_sane_readahead(ra->ra_pages); - if (ra_pages) { - ra->start = max_t(long, 0, offset - ra_pages/2); - ra->size = ra_pages; - ra->async_size = 0; - ra_submit(ra, mapping, file); - } + ra->start = max_t(long, 0, offset - ra_pages / 2); + ra->size = ra_pages; + ra->async_size = 0; + ra_submit(ra, mapping, file); } /* From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id A840490010B for ; Fri, 29 Apr 2011 23:31:44 -0400 (EDT) Message-Id: <20110430033017.923224207@intel.com> Date: Sat, 30 Apr 2011 11:22:44 +0800 From: Wu Fengguang Subject: [PATCH 1/3] readahead: return early when readahead is disabled References: <20110430032243.355805181@intel.com> Content-Disposition: inline; filename=readahead-early-abort-mmap-around.patch Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Andi Kleen Cc: Tim Chen , Wu Fengguang , Li Shaohua , LKML , Linux Memory Management List Reduce readahead overheads by returning early in do_sync_mmap_readahead(). tmpfs has ra_pages=0 and it can page fault really fast (not constraint by IO if not swapping). Tested-by: Tim Chen Reported-by: Andi Kleen Signed-off-by: Wu Fengguang --- mm/filemap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- linux-next.orig/mm/filemap.c 2011-04-23 08:56:59.000000000 +0800 +++ linux-next/mm/filemap.c 2011-04-23 09:01:44.000000000 +0800 @@ -1528,6 +1528,8 @@ static void do_sync_mmap_readahead(struc /* If we don't want any read-ahead, don't bother */ if (VM_RandomReadHint(vma)) return; + if (!ra->ra_pages) + return; if (VM_SequentialReadHint(vma) || offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { @@ -1550,12 +1552,10 @@ static void do_sync_mmap_readahead(struc * mmap read-around */ ra_pages = max_sane_readahead(ra->ra_pages); - if (ra_pages) { - ra->start = max_t(long, 0, offset - ra_pages/2); - ra->size = ra_pages; - ra->async_size = 0; - ra_submit(ra, mapping, file); - } + ra->start = max_t(long, 0, offset - ra_pages / 2); + ra->size = ra_pages; + ra->async_size = 0; + ra_submit(ra, mapping, file); } /* -- 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