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,URIBL_BLOCKED,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 D092EC65C22 for ; Fri, 2 Nov 2018 12:33:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A236D20831 for ; Fri, 2 Nov 2018 12:33:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A236D20831 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 S1727485AbeKBVks (ORCPT ); Fri, 2 Nov 2018 17:40:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:40032 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726008AbeKBVks (ORCPT ); Fri, 2 Nov 2018 17:40:48 -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 27C8FABEF; Fri, 2 Nov 2018 12:33:45 +0000 (UTC) Date: Fri, 2 Nov 2018 13:32:52 +0100 From: Michal Hocko To: Balbir Singh Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hotplug: Optimize clear_hwpoisoned_pages Message-ID: <20181102120856.GC28039@dhcp22.suse.cz> References: <20181102120001.4526-1-bsingharora@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181102120001.4526-1-bsingharora@gmail.com> 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 02-11-18 23:00:01, Balbir Singh wrote: > In hot remove, we try to clear poisoned pages, but > a small optimization to check if num_poisoned_pages > is 0 helps remove the iteration through nr_pages. > > Signed-off-by: Balbir Singh Makes sense to me. It would be great to actually have some number but the optimization for the normal case is quite obvious. Acked-by: Michal Hocko > --- > mm/sparse.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 33307fc05c4d..16219c7ddb5f 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -724,6 +724,16 @@ static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > if (!memmap) > return; > > + /* > + * A further optimization is to have per section > + * ref counted num_poisoned_pages, but that is going > + * to need more space per memmap, for now just do > + * a quick global check, this should speed up this > + * routine in the absence of bad pages. > + */ > + if (atomic_long_read(&num_poisoned_pages) == 0) > + return; > + > for (i = 0; i < nr_pages; i++) { > if (PageHWPoison(&memmap[i])) { > atomic_long_sub(1, &num_poisoned_pages); > -- > 2.17.1 > -- Michal Hocko SUSE Labs