Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758678AbZCPQwc (ORCPT ); Mon, 16 Mar 2009 12:52:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754961AbZCPQwX (ORCPT ); Mon, 16 Mar 2009 12:52:23 -0400 Received: from gir.skynet.ie ([193.1.99.77]:50793 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752408AbZCPQwX (ORCPT ); Mon, 16 Mar 2009 12:52:23 -0400 Date: Mon, 16 Mar 2009 16:52:20 +0000 From: Mel Gorman To: Christoph Lameter Cc: Linux Memory Management List , Pekka Enberg , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra Subject: Re: [PATCH 31/35] Optimistically check the first page on the PCP free list is suitable Message-ID: <20090316165220.GO24293@csn.ul.ie> References: <1237196790-7268-1-git-send-email-mel@csn.ul.ie> <1237196790-7268-32-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 38 On Mon, Mar 16, 2009 at 12:33:44PM -0400, Christoph Lameter wrote: > On Mon, 16 Mar 2009, Mel Gorman wrote: > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index bb5bd5e..8568284 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1212,6 +1212,12 @@ again: > > if (pcp_page_suit(page, order)) > > break; > > } else { > > + /* Optimistic before we start a list search */ > > + page = list_entry(list->next, struct page, lru); > > + if (pcp_page_suit(page, order)) > > + goto found; > > + > > + /* Do the search */ > > list_for_each_entry(page, list, lru) > > if (pcp_page_suit(page, order)) > > break; > > I am not convinced that this is beneficial. If it would then the compiler > would unroll the loop. > It hit a large number of times when I checked (although I don't have the figures any more) and the list_for_each_entry() does a prefetch possibly fetching in a line we don't need. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/