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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 E3A5CC18DF5 for ; Tue, 20 Nov 2018 14:19:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E836206BA for ; Tue, 20 Nov 2018 14:18:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E836206BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1729749AbeKUAsH (ORCPT ); Tue, 20 Nov 2018 19:48:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43702 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726896AbeKUAsG (ORCPT ); Tue, 20 Nov 2018 19:48:06 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 04D1DC058CA6; Tue, 20 Nov 2018 14:18:44 +0000 (UTC) Received: from [10.36.117.138] (ovpn-117-138.ams2.redhat.com [10.36.117.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 667626A68F; Tue, 20 Nov 2018 14:18:42 +0000 (UTC) Subject: Re: [RFC PATCH 1/3] mm, memory_hotplug: try to migrate full section worth of pages To: Michal Hocko , linux-mm@kvack.org Cc: Andrew Morton , Oscar Salvador , Pavel Tatashin , LKML , Michal Hocko References: <20181120134323.13007-1-mhocko@kernel.org> <20181120134323.13007-2-mhocko@kernel.org> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181120134323.13007-2-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 20 Nov 2018 14:18:44 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.11.18 14:43, Michal Hocko wrote: > From: Michal Hocko > > do_migrate_range has been limiting the number of pages to migrate to 256 > for some reason which is not documented. Even if the limit made some > sense back then when it was introduced it doesn't really serve a good > purpose these days. If the range contains huge pages then > we break out of the loop too early and go through LRU and pcp > caches draining and scan_movable_pages is quite suboptimal. > > The only reason to limit the number of pages I can think of is to reduce > the potential time to react on the fatal signal. But even then the > number of pages is a questionable metric because even a single page > might migration block in a non-killable state (e.g. __unmap_and_move). > > Remove the limit and offline the full requested range (this is one > membblock worth of pages with the current code). Should we ever get a > report that offlining takes too long to react on fatal signal then we > should rather fix the core migration to use killable waits and bailout > on a signal. > > Signed-off-by: Michal Hocko > --- > mm/memory_hotplug.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index c82193db4be6..6263c8cd4491 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1339,18 +1339,16 @@ static struct page *new_node_page(struct page *page, unsigned long private) > return new_page_nodemask(page, nid, &nmask); > } > > -#define NR_OFFLINE_AT_ONCE_PAGES (256) > static int > do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > { > unsigned long pfn; > struct page *page; > - int move_pages = NR_OFFLINE_AT_ONCE_PAGES; > int not_managed = 0; > int ret = 0; > LIST_HEAD(source); > > - for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) { > + for (pfn = start_pfn; pfn < end_pfn; pfn++) { > if (!pfn_valid(pfn)) > continue; > page = pfn_to_page(pfn); > @@ -1362,8 +1360,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > ret = -EBUSY; > break; > } > - if (isolate_huge_page(page, &source)) > - move_pages -= 1 << compound_order(head); > + isolate_huge_page(page, &source); > continue; > } else if (PageTransHuge(page)) > pfn = page_to_pfn(compound_head(page)) > @@ -1382,7 +1379,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > if (!ret) { /* Success */ > put_page(page); > list_add_tail(&page->lru, &source); > - move_pages--; > if (!__PageMovable(page)) > inc_node_page_state(page, NR_ISOLATED_ANON + > page_is_file_cache(page)); > Yes, there is basically no statement why it was done that way. If it is important, there should be one. (we could also check for pending signals inside that function if really required) Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb