From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 2F9C96B00E9 for ; Sat, 9 Jul 2011 16:53:10 -0400 (EDT) Date: Sat, 9 Jul 2011 13:53:08 -0700 From: Wu Fengguang Subject: Re: [PATCH 3/3] mm/readahead: Move the check for ra_pages after VM_SequentialReadHint() Message-ID: <20110709205308.GC17463@localhost> References: <323ddfc402a7f7b94f0cb02bba15acb2acca786f.1310239575.git.rprabhu@wnohang.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <323ddfc402a7f7b94f0cb02bba15acb2acca786f.1310239575.git.rprabhu@wnohang.net> Sender: owner-linux-mm@kvack.org List-ID: To: Raghavendra D Prabhu Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , Raghavendra D Prabhu On Sun, Jul 10, 2011 at 03:41:20AM +0800, Raghavendra D Prabhu wrote: > page_cache_sync_readahead checks for ra->ra_pages again, so moving the check after VM_SequentialReadHint. NAK. This patch adds nothing but overheads. > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1566,8 +1566,6 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma, > /* 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)) { > page_cache_sync_readahead(mapping, ra, file, offset, > @@ -1575,6 +1573,9 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma, > return; > } > > + if (!ra->ra_pages) > + return; > + page_cache_sync_readahead() has the same if (!ra->ra_pages) return; So the patch adds the call into page_cache_sync_readahead() just to return.. Thanks, Fengguang -- 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