From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751518AbZH1Nqy (ORCPT ); Fri, 28 Aug 2009 09:46:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751160AbZH1Nqx (ORCPT ); Fri, 28 Aug 2009 09:46:53 -0400 Received: from mail-gx0-f205.google.com ([209.85.217.205]:59095 "EHLO mail-gx0-f205.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbZH1Nqw convert rfc822-to-8bit (ORCPT ); Fri, 28 Aug 2009 09:46:52 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=tChTD2YqSIsR3tE+UedE2u0aGJqomGkQpbFCCzc5IMzQNtdA9jPq0IkS14JVqxzUBR bAeIrVDdhPi/fahauoM4Ir3mZdDx8a7BoDRHlGI55I3oMruHnmEfgCHNwVjMfoa0cPgS 6SxHqJ0UOo3/XEnvRtzlq/g++BtshuPIsJ0PI= MIME-Version: 1.0 In-Reply-To: <20090828125559.GD5054@csn.ul.ie> References: <1251449067-3109-1-git-send-email-mel@csn.ul.ie> <1251449067-3109-2-git-send-email-mel@csn.ul.ie> <20090828205241.fc8dfa51.minchan.kim@barrios-desktop> <28c262360908280500tb47685btc9f36ca81605d55@mail.gmail.com> <20090828125559.GD5054@csn.ul.ie> Date: Fri, 28 Aug 2009 22:46:54 +0900 Message-ID: <28c262360908280646s506db2ccsa3842ee33b241120@mail.gmail.com> Subject: Re: [PATCH 1/2] page-allocator: Split per-cpu list into one-list-per-migrate-type From: Minchan Kim To: Mel Gorman Cc: Andrew Morton , Linux Memory Management List , Christoph Lameter , Nick Piggin , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 28, 2009 at 9:56 PM, Mel Gorman wrote: > On Fri, Aug 28, 2009 at 09:00:25PM +0900, Minchan Kim wrote: >> On Fri, Aug 28, 2009 at 8:52 PM, Minchan Kim wrote: >> > Hi, Mel. >> > >> > On Fri, 28 Aug 2009 09:44:26 +0100 >> > Mel Gorman wrote: >> > >> >> Currently the per-cpu page allocator searches the PCP list for pages of the >> >> correct migrate-type to reduce the possibility of pages being inappropriate >> >> placed from a fragmentation perspective. This search is potentially expensive >> >> in a fast-path and undesirable. Splitting the per-cpu list into multiple >> >> lists increases the size of a per-cpu structure and this was potentially >> >> a major problem at the time the search was introduced. These problem has >> >> been mitigated as now only the necessary number of structures is allocated >> >> for the running system. >> >> >> >> This patch replaces a list search in the per-cpu allocator with one list per >> >> migrate type. The potential snag with this approach is when bulk freeing >> >> pages. We round-robin free pages based on migrate type which has little >> >> bearing on the cache hotness of the page and potentially checks empty lists >> >> repeatedly in the event the majority of PCP pages are of one type. >> >> >> >> Signed-off-by: Mel Gorman >> >> Acked-by: Nick Piggin Reviewed-by: Minchan Kim >> >>   */ >> >> -static void free_pages_bulk(struct zone *zone, int count, >> >> -                                     struct list_head *list, int order) >> >> +static void free_pcppages_bulk(struct zone *zone, int count, >> >> +                                     struct per_cpu_pages *pcp) >> >>  { >> >> +     int migratetype = 0; >> >> + >> > >> > How about caching the last sucess migratetype >> > with 'per_cpu_pages->last_alloc_type'? >>                                          ^^^^ >>                                          free >> > I think it could prevent a litte spinning empty list. >> >> Anyway, Ignore me. >> I didn't see your next patch. >> > > Nah, it's a reasonable suggestion. Patch 2 was one effort to reduce > spinning but the comment was in patch 1 in case someone thought of > something better. I tried what you suggested before but it didn't work > out. For any sort of workload that varies the type of allocation (very > frequent), it didn't reduce spinning significantly. Thanks for good information. > -- > Mel Gorman > Part-time Phd Student                          Linux Technology Center > University of Limerick                         IBM Dublin Software Lab > -- Kind regards, Minchan Kim