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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 238D8C32751 for ; Wed, 31 Jul 2019 12:07:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF02A2089E for ; Wed, 31 Jul 2019 12:07:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728887AbfGaMG7 (ORCPT ); Wed, 31 Jul 2019 08:06:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:33900 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726894AbfGaMG7 (ORCPT ); Wed, 31 Jul 2019 08:06:59 -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 F2DA5AB9D; Wed, 31 Jul 2019 12:06:55 +0000 (UTC) Subject: Re: [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY_PRIORITY everywhere for costly orders To: Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hillf Danton , Michal Hocko , Mel Gorman , Johannes Weiner , Andrew Morton References: <20190724175014.9935-1-mike.kravetz@oracle.com> <20190724175014.9935-3-mike.kravetz@oracle.com> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= mQINBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 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xVKRSg3I2m+DUTVqBy7Lixo73hnW69kSjtqCeamY/NSu6LNP+b0wAOKhwz9hBEwEHLp05+mj 5ZFJyfGsOiNUcMoO/17FO4EBxSDP3FDLllpuzlFD7SXkfJaMWYmXIlO0jLzdfwfcnDzBbPwO hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: <278da9d8-6781-b2bc-8de6-6a71e879513c@suse.cz> Date: Wed, 31 Jul 2019 14:06:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190724175014.9935-3-mike.kravetz@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/24/19 7:50 PM, Mike Kravetz wrote: > For PAGE_ALLOC_COSTLY_ORDER allocations, MIN_COMPACT_COSTLY_PRIORITY is > minimum (highest priority). Other places in the compaction code key off > of MIN_COMPACT_PRIORITY. Costly order allocations will never get to > MIN_COMPACT_PRIORITY. Therefore, some conditions will never be met for > costly order allocations. > > This was observed when hugetlb allocations could stall for minutes or > hours when should_compact_retry() would return true more often then it > should. Specifically, this was in the case where compact_result was > COMPACT_DEFERRED and COMPACT_PARTIAL_SKIPPED and no progress was being > made. Hmm, the point of MIN_COMPACT_COSTLY_PRIORITY was that costly allocations will not reach the priority where compaction becomes too expensive. With your patch, they still don't reach that priority value, but are allowed to be thorough anyway, even sooner. That just seems like a wrong way to fix the problem. If should_compact_retry() returns misleading results for costly allocations, then that should be fixed instead? Alternatively, you might want to say that hugetlb allocations are not like other random costly allocations, because the admin setting nr_hugepages is prepared to take the cost (I thought that was indicated by the __GFP_RETRY_MAYFAIL flag, but seeing all the other users of it, I'm not sure anymore). In that case should_compact_retry() could take __GFP_RETRY_MAYFAIL into account and allow MIN_COMPACT_PRIORITY even for costly allocations. > Signed-off-by: Mike Kravetz > --- > mm/compaction.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 952dc2fb24e5..325b746068d1 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2294,9 +2294,15 @@ static enum compact_result compact_zone_order(struct zone *zone, int order, > .alloc_flags = alloc_flags, > .classzone_idx = classzone_idx, > .direct_compaction = true, > - .whole_zone = (prio == MIN_COMPACT_PRIORITY), > - .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), > - .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) > + .whole_zone = ((order > PAGE_ALLOC_COSTLY_ORDER) ? > + (prio == MIN_COMPACT_COSTLY_PRIORITY) : > + (prio == MIN_COMPACT_PRIORITY)), > + .ignore_skip_hint = ((order > PAGE_ALLOC_COSTLY_ORDER) ? > + (prio == MIN_COMPACT_COSTLY_PRIORITY) : > + (prio == MIN_COMPACT_PRIORITY)), > + .ignore_block_suitable = ((order > PAGE_ALLOC_COSTLY_ORDER) ? > + (prio == MIN_COMPACT_COSTLY_PRIORITY) : > + (prio == MIN_COMPACT_PRIORITY)) > }; > struct capture_control capc = { > .cc = &cc, > @@ -2338,6 +2344,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, > int may_perform_io = gfp_mask & __GFP_IO; > struct zoneref *z; > struct zone *zone; > + int min_priority; > enum compact_result rc = COMPACT_SKIPPED; > > /* > @@ -2350,12 +2357,13 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, > trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio); > > /* Compact each zone in the list */ > + min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ? > + MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY; > for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, > ac->nodemask) { > enum compact_result status; > > - if (prio > MIN_COMPACT_PRIORITY > - && compaction_deferred(zone, order)) { > + if (prio > min_priority && compaction_deferred(zone, order)) { > rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); > continue; > } >