From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id D346990010D for ; Fri, 29 Apr 2011 23:31:44 -0400 (EDT) Message-Id: <20110430033018.169293004@intel.com> Date: Sat, 30 Apr 2011 11:22:46 +0800 From: Wu Fengguang Subject: [PATCH 3/3] readahead: trigger mmap sequential readahead on PG_readahead References: <20110430032243.355805181@intel.com> Content-Disposition: inline; filename=readahead-no-mmap-prev_pos.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 Previously the mmap sequential readahead is triggered by updating ra->prev_pos on each page fault and compare it with current page offset. It costs dirtying the cache line on each _minor_ page fault. So remove the ra->prev_pos recording, and instead tag PG_readahead to trigger the possible sequential readahead. It's not only more simple, but also will work more reliably and reduce cache line bouncing on concurrent page faults on shared struct file. Tested-by: Tim Chen Reported-by: Andi Kleen Signed-off-by: Wu Fengguang --- mm/filemap.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- linux-next.orig/mm/filemap.c 2011-04-23 16:52:21.000000000 +0800 +++ linux-next/mm/filemap.c 2011-04-24 09:59:08.000000000 +0800 @@ -1531,8 +1531,7 @@ static void do_sync_mmap_readahead(struc if (!ra->ra_pages) return; - if (VM_SequentialReadHint(vma) || - offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { + if (VM_SequentialReadHint(vma)) { page_cache_sync_readahead(mapping, ra, file, offset, ra->ra_pages); return; @@ -1555,7 +1554,7 @@ static void do_sync_mmap_readahead(struc ra_pages = max_sane_readahead(ra->ra_pages); ra->start = max_t(long, 0, offset - ra_pages / 2); ra->size = ra_pages; - ra->async_size = 0; + ra->async_size = ra_pages / 4; ra_submit(ra, mapping, file); } @@ -1661,7 +1660,6 @@ retry_find: return VM_FAULT_SIGBUS; } - ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT; vmf->page = page; return ret | VM_FAULT_LOCKED; -- 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