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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 5348ECA9EBD for ; Fri, 25 Oct 2019 08:21:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B5A021872 for ; Fri, 25 Oct 2019 08:21:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U3w9oqu0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408136AbfJYIVo (ORCPT ); Fri, 25 Oct 2019 04:21:44 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:60931 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2405453AbfJYIVn (ORCPT ); Fri, 25 Oct 2019 04:21:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571991701; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fHKlI7wnW8uMQDoEoj1c5yaGeprsprURO6IlKm0Z6Aw=; b=U3w9oqu0CAPcYh5mdazxLFaBCZGGePPPVWHV971I7Ok6N6aDmlvdLXJd0NCLVs/VLdKCPf 0Oxx0wMG1u1y1Jlmav9AbBCFbnecWLusqz7ItNrblrIF6+dacWlz/WfcjoN71U7oyRAHVj p0tVuHn2DpqxcMv1p2+/PpbK8iQiweM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-14-qKISDm60Oe6kVLJK0KRPDA-1; Fri, 25 Oct 2019 04:21:38 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9582A1800E00; Fri, 25 Oct 2019 08:21:36 +0000 (UTC) Received: from [10.36.116.205] (ovpn-116-205.ams2.redhat.com [10.36.116.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id F071D1001B28; Fri, 25 Oct 2019 08:21:28 +0000 (UTC) Subject: Re: [PATCH 2/2] mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo To: Michal Hocko , Andrew Morton , Mel Gorman , Waiman Long Cc: Johannes Weiner , Roman Gushchin , Vlastimil Babka , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , linux-mm@kvack.org, LKML , Michal Hocko References: <20191025072610.18526-1-mhocko@kernel.org> <20191025072610.18526-3-mhocko@kernel.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <10350bd9-a0ba-9ba9-82a8-99588acf2312@redhat.com> Date: Fri, 25 Oct 2019 10:21:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191025072610.18526-3-mhocko@kernel.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: qKISDm60Oe6kVLJK0KRPDA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25.10.19 09:26, Michal Hocko wrote: > From: Michal Hocko >=20 > pagetypeinfo_showfree_print is called by zone->lock held in irq mode. > This is not really nice because it blocks both any interrupts on that > cpu and the page allocator. On large machines this might even trigger > the hard lockup detector. >=20 > Considering the pagetypeinfo is a debugging tool we do not really need > exact numbers here. The primary reason to look at the outuput is to see > how pageblocks are spread among different migratetypes and low number of > pages is much more interesting therefore putting a bound on the number > of pages on the free_list sounds like a reasonable tradeoff. >=20 > The new output will simply tell > [...] > Node 6, zone Normal, type Movable >100000 >100000 >100000 >1000= 00 41019 31560 23996 10054 3229 983 648 >=20 > instead of > Node 6, zone Normal, type Movable 399568 294127 221558 102119 = 41019 31560 23996 10054 3229 983 648 >=20 > The limit has been chosen arbitrary and it is a subject of a future > change should there be a need for that. >=20 > While we are at it, also drop the zone lock after each free_list > iteration which will help with the IRQ and page allocator responsiveness > even further as the IRQ lock held time is always bound to those 100k > pages. >=20 > Suggested-by: Andrew Morton > Reviewed-by: Waiman Long > Signed-off-by: Michal Hocko > --- > mm/vmstat.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) >=20 > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 4e885ecd44d1..ddb89f4e0486 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -1383,12 +1383,29 @@ static void pagetypeinfo_showfree_print(struct se= q_file *m, > =09=09=09unsigned long freecount =3D 0; > =09=09=09struct free_area *area; > =09=09=09struct list_head *curr; > +=09=09=09bool overflow =3D false; > =20 > =09=09=09area =3D &(zone->free_area[order]); > =20 > -=09=09=09list_for_each(curr, &area->free_list[mtype]) > -=09=09=09=09freecount++; > -=09=09=09seq_printf(m, "%6lu ", freecount); > +=09=09=09list_for_each(curr, &area->free_list[mtype]) { > +=09=09=09=09/* > +=09=09=09=09 * Cap the free_list iteration because it might > +=09=09=09=09 * be really large and we are under a spinlock > +=09=09=09=09 * so a long time spent here could trigger a > +=09=09=09=09 * hard lockup detector. Anyway this is a > +=09=09=09=09 * debugging tool so knowing there is a handful > +=09=09=09=09 * of pages in this order should be more than "of this order" ? > +=09=09=09=09 * sufficient s/sufficient"/sufficient." ? > +=09=09=09=09 */ > +=09=09=09=09if (++freecount >=3D 100000) { > +=09=09=09=09=09overflow =3D true; > +=09=09=09=09=09break; > +=09=09=09=09} > +=09=09=09} > +=09=09=09seq_printf(m, "%s%6lu ", overflow ? ">" : "", freecount); > +=09=09=09spin_unlock_irq(&zone->lock); > +=09=09=09cond_resched(); > +=09=09=09spin_lock_irq(&zone->lock); > =09=09} > =09=09seq_putc(m, '\n'); > =09} >=20 Acked-by: David Hildenbrand --=20 Thanks, David / dhildenb