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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 B54C4C433E2 for ; Wed, 9 Sep 2020 11:30:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 847F52074B for ; Wed, 9 Sep 2020 11:30:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728936AbgIILaM (ORCPT ); Wed, 9 Sep 2020 07:30:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:57422 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728297AbgIIL2a (ORCPT ); Wed, 9 Sep 2020 07:28:30 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6DAE0B1A9; Wed, 9 Sep 2020 11:27:43 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 09 Sep 2020 13:27:42 +0200 From: osalvador@suse.de To: Vlastimil Babka Cc: David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Pavel Tatashin , Joonsoo Kim Subject: Re: [RFC 0/5] disable pcplists during page isolation In-Reply-To: References: <20200907163628.26495-1-vbabka@suse.cz> <0ffb1c2d-1b28-23f7-53e1-63e6f0f4cd41@redhat.com> User-Agent: Roundcube Webmail Message-ID: <3f4bd7b0c73f59b4cd2adaad3ccc38bf@suse.de> X-Sender: osalvador@suse.de Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-09-09 12:54, Vlastimil Babka wrote: > Thanks! I expect no performance change while no isolation is in > progress, as > there are no new tests added in alloc/free paths. During page isolation > there's > a single drain instead of once-per-pageblock, which is a benefit. But > the > pcplists are effectively disabled for the whole of online_pages(), > offline_pages() or alloc_contig_range(), which will affect parallel > page > allocator users. It depends on how long these operations take and how > heavy the > parallel usage is, so I have no good answers. Might be similar to the > current > periodic drain. I have seen some systems taking quite some time when offlining sections due to the migration of the respective pages not being that smooth and having do_migrate_range to do some spins. But to be fair, online_pages and offline_pages are not routines that get called that often, and we would be safe to assume that memory-hotplug operations are not constantly happening, but are rather one-offs operations. I am not sure about Xen and HV, IIRC Xen was using online_pages and offline_pages routines to do the ballooning? I will dive in this in the following days, thanks for the work Vlastimil