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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 9D584C04EB9 for ; Thu, 6 Dec 2018 09:26:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5DB6920850 for ; Thu, 6 Dec 2018 09:26:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5DB6920850 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz 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 S1729353AbeLFJ0R (ORCPT ); Thu, 6 Dec 2018 04:26:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:55130 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727575AbeLFJ0R (ORCPT ); Thu, 6 Dec 2018 04:26:17 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4DC57AFBE; Thu, 6 Dec 2018 09:26:13 +0000 (UTC) Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression To: Andrea Arcangeli , David Rientjes Cc: Linus Torvalds , mgorman@techsingularity.net, mhocko@kernel.org, ying.huang@intel.com, s.priebe@profihost.ag, Linux List Kernel Mailing , alex.williamson@redhat.com, lkp@01.org, kirill@shutemov.name, Andrew Morton , zi.yan@cs.rutgers.edu References: <20181203201214.GB3540@redhat.com> <64a4aec6-3275-a716-8345-f021f6186d9b@suse.cz> <20181204104558.GV23260@techsingularity.net> <20181205204034.GB11899@redhat.com> <20181205233632.GE11899@redhat.com> <20181206005425.GB21159@redhat.com> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.2 MIME-Version: 1.0 In-Reply-To: <20181206005425.GB21159@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/6/18 1:54 AM, Andrea Arcangeli wrote: > On Wed, Dec 05, 2018 at 04:18:14PM -0800, David Rientjes wrote: >> On Wed, 5 Dec 2018, Andrea Arcangeli wrote: >> >> Note that in addition to COMPACT_SKIPPED that you mention, compaction can >> fail with COMPACT_COMPLETE, meaning the full scan has finished without >> freeing a hugepage, or COMPACT_DEFERRED, meaning that doing another scan >> is unlikely to produce a different result. COMPACT_SKIPPED makes sense to >> do reclaim if it can become accessible to isolate_freepages() and >> hopefully another allocator does not allocate from these newly freed pages >> before compaction can scan the zone again. For COMPACT_COMPLETE and >> COMPACT_DEFERRED, reclaim is unlikely to ever help. > > The COMPACT_COMPLETE and (COMPACT_PARTIAL_SKIPPED for that matter) > seems just a mistake in the max() evaluation try_to_compact_pages() > that let it return COMPACT_COMPLETE and COMPACT_PARTIAL_SKIPPED. I > think it should just return COMPACT_DEFERRED in those two cases and it > should be enforced forced for all prio. > > There are really only 3 cases that matter for the caller: > > 1) succeed -> we got the page > 2) defer -> we failed (caller won't care about why) > 3) skipped -> failed because not enough 4k freed -> reclaim must be invoked then > compaction can be retried > > PARTIAL_SKIPPED/COMPLETE both fall into 2) above so for the caller > they should be treated the same way. It doesn't seem very concerning > that it may try like if it succeeded and do a spurious single reclaim > invocation, but it's good to fix this and take the COMPACT_DEFERRED > nopage path in the __GFP_NORETRY case. Yeah good point. I wouldn't change the general logic of try_to_compact_pages() though, but the condition for __GFP_NORETRY can simply change to: if (compact_result != COMPACT_SKIPPED) goto nopage; I can make a patch ASAP together with a few others I think are needed, that should hopefully avoid the need for __GFP_COMPACT_ONLY or checks based on order. What's probably unavoidable though is adding back __GFP_NORETRY for madvised allocations (i.e. partially reverting 2516035499b95), but David was fine with that and your __GFP_ONLY_COMPACT approach effectively did it too.