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=-8.2 required=3.0 tests=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 B676FC433FF for ; Wed, 31 Jul 2019 11:08:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BFDE208C3 for ; Wed, 31 Jul 2019 11:08:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728231AbfGaLIt (ORCPT ); Wed, 31 Jul 2019 07:08:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:43142 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725793AbfGaLIs (ORCPT ); Wed, 31 Jul 2019 07:08:48 -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 C72B0AF1B; Wed, 31 Jul 2019 11:08:45 +0000 (UTC) Subject: Re: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection To: Hillf Danton , Mel Gorman , Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Johannes Weiner , Andrew Morton References: <20190724175014.9935-1-mike.kravetz@oracle.com> <20190724175014.9935-2-mike.kravetz@oracle.com> <20190725080551.GB2708@suse.de> 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: <295a37b1-8257-9b4a-b586-9a4990cc9d35@suse.cz> Date: Wed, 31 Jul 2019 13:08:44 +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: <20190725080551.GB2708@suse.de> Content-Type: text/plain; charset=iso-8859-15 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 7/26/19 9:40 AM, Hillf Danton wrote: > > On Thu, 25 Jul 2019 08:05:55 +0000 (UTC) Mel Gorman wrote: >> >> Agreed that the description could do with improvement. However, it >> makes sense that if compaction reports it can make progress that it is >> unnecessary to continue reclaiming. > > Thanks Mike and Mel. > > Hillf > ---8<--- > From: Hillf Danton > Subject: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection > > Address the issue of should_continue_reclaim continuing true too often > for __GFP_RETRY_MAYFAIL attempts when !nr_reclaimed and nr_scanned. > This could happen during hugetlb page allocation causing stalls for > minutes or hours. > > We can stop reclaiming pages if compaction reports it can make a progress. > A code reshuffle is needed to do that. And it has side-effects, however, > with allocation latencies in other cases but that would come at the cost > of potential premature reclaim which has consequences of itself. I don't really understand that paragraph, did Mel meant it like this? > We can also bail out of reclaiming pages if we know that there are not > enough inactive lru pages left to satisfy the costly allocation. > > We can give up reclaiming pages too if we see dryrun occur, with the > certainty of plenty of inactive pages. IOW with dryrun detected, we are > sure we have reclaimed as many pages as we could. > > Cc: Mike Kravetz > Cc: Mel Gorman > Cc: Michal Hocko > Cc: Vlastimil Babka > Cc: Johannes Weiner > Signed-off-by: Hillf Danton I agree this is an improvement overall, but perhaps the patch does too many things at once. The reshuffle is one thing and makes sense. The change of the last return condition could perhaps be separate. Also AFAICS the ultimate result is that when nr_reclaimed == 0, the function will now always return false. Which makes the initial test for __GFP_RETRY_MAYFAIL and the comments there misleading. There will no longer be a full LRU scan guaranteed - as long as the scanned LRU chunk yields no reclaimed page, we abort. > --- > mm/vmscan.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f4fd02a..484b6b1 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2673,18 +2673,6 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, > return false; > } > > - /* > - * If we have not reclaimed enough pages for compaction and the > - * inactive lists are large enough, continue reclaiming > - */ > - pages_for_compaction = compact_gap(sc->order); > - inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); > - if (get_nr_swap_pages() > 0) > - inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); > - if (sc->nr_reclaimed < pages_for_compaction && > - inactive_lru_pages > pages_for_compaction) > - return true; > - > /* If compaction would go ahead or the allocation would succeed, stop */ > for (z = 0; z <= sc->reclaim_idx; z++) { > struct zone *zone = &pgdat->node_zones[z]; > @@ -2700,7 +2688,21 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, > ; > } > } > - return true; > + > + /* > + * If we have not reclaimed enough pages for compaction and the > + * inactive lists are large enough, continue reclaiming > + */ > + pages_for_compaction = compact_gap(sc->order); > + inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); > + if (get_nr_swap_pages() > 0) > + inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); > + > + return inactive_lru_pages > pages_for_compaction && > + /* > + * avoid dryrun with plenty of inactive pages > + */ > + nr_scanned && nr_reclaimed; > } > > static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg) > -- >