From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FD29C64EAD for ; Tue, 9 Oct 2018 09:30:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B8AE2150C for ; Tue, 9 Oct 2018 09:30:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2B8AE2150C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726781AbeJIQqj (ORCPT ); Tue, 9 Oct 2018 12:46:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:53584 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726722AbeJIQqj (ORCPT ); Tue, 9 Oct 2018 12:46:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B3DD5AF6A; Tue, 9 Oct 2018 09:30:37 +0000 (UTC) Date: Tue, 9 Oct 2018 11:30:37 +0200 From: Michal Hocko To: Arun KS Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, boris.ostrovsky@oracle.com, jgross@suse.com, akpm@linux-foundation.org, dan.j.williams@intel.com, vbabka@suse.cz, iamjoonsoo.kim@lge.com, gregkh@linuxfoundation.org, osalvador@suse.de, malat@debian.org, kirill.shutemov@linux.intel.com, jrdr.linux@gmail.com, yasu.isimatu@gmail.com, mgorman@techsingularity.net, aaron.lu@intel.com, devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, xen-devel@lists.xenproject.org, vatsa@codeaurora.org, vinmenon@codeaurora.org, getarunks@gmail.com Subject: Re: [PATCH v5 2/2] mm/page_alloc: remove software prefetching in __free_pages_core Message-ID: <20181009093037.GI8528@dhcp22.suse.cz> References: <1538727006-5727-1-git-send-email-arunks@codeaurora.org> <1538727006-5727-2-git-send-email-arunks@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1538727006-5727-2-git-send-email-arunks@codeaurora.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 05-10-18 13:40:06, Arun KS wrote: > They not only increase the code footprint, they actually make things > slower rather than faster. Remove them as contemporary hardware doesn't > need any hint. I agree with the change but it is much better to add some numbers whenever arguing about performance impact. > > Suggested-by: Dan Williams > Signed-off-by: Arun KS > --- > mm/page_alloc.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7ab5274..90db431 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1258,14 +1258,10 @@ void __free_pages_core(struct page *page, unsigned int order) > struct page *p = page; > unsigned int loop; > > - prefetchw(p); > - for (loop = 0; loop < (nr_pages - 1); loop++, p++) { > - prefetchw(p + 1); > + for (loop = 0; loop < nr_pages ; loop++, p++) { > __ClearPageReserved(p); > set_page_count(p, 0); > } > - __ClearPageReserved(p); > - set_page_count(p, 0); > > page_zone(page)->managed_pages += nr_pages; > set_page_refcounted(page); > -- > 1.9.1 > -- Michal Hocko SUSE Labs