From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 4E3C18E0001 for ; Wed, 19 Dec 2018 08:29:37 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id e17so16272772edr.7 for ; Wed, 19 Dec 2018 05:29:37 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id h34sor11087390edb.28.2018.12.19.05.29.35 for (Google Transport Security); Wed, 19 Dec 2018 05:29:35 -0800 (PST) Date: Wed, 19 Dec 2018 13:29:34 +0000 From: Wei Yang Subject: Re: [PATCH v2] mm, page_isolation: remove drain_all_pages() in set_migratetype_isolate() Message-ID: <20181219132934.65vymftfgd2atcxa@master> Reply-To: Wei Yang References: <20181214023912.77474-1-richard.weiyang@gmail.com> <20181218204656.4297-1-richard.weiyang@gmail.com> <20181219095110.GB5758@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181219095110.GB5758@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Wei Yang , linux-mm@kvack.org, akpm@linux-foundation.org, osalvador@suse.de, david@redhat.com On Wed, Dec 19, 2018 at 10:51:10AM +0100, Michal Hocko wrote: >On Wed 19-12-18 04:46:56, Wei Yang wrote: >> Below is a brief call flow for __offline_pages() and >> alloc_contig_range(): >> >> __offline_pages()/alloc_contig_range() >> start_isolate_page_range() >> set_migratetype_isolate() >> drain_all_pages() >> drain_all_pages() >> >> Current logic is: isolate and drain pcp list for each pageblock and >> drain pcp list again. This is not necessary and we could just drain pcp >> list once after isolate this whole range. >> >> The reason is start_isolate_page_range() will set the migrate type of >> a range to MIGRATE_ISOLATE. After doing so, this range will never be >> allocated from Buddy, neither to a real user nor to pcp list. > >But it is important to note that those pages still can be allocated from >the pcp lists until we do drain_all_pages(). > >One thing that I really do not like about this patch (and I believe I >have mentioned that previously) that you rely on callers to do the right >thing. The proper fix would be to do the draining in >start_isolate_page_range and remove them from callers. Also what does Well, I don't really understand this meaning previously. So you prefer set_migratetype_isolate() do the drain instead of the caller (__offline_pages) do the drain. Is my understanding correct? >prevent start_isolate_page_range to work on multiple zones? At least >contiguous allocator can do that in principle. As the comment mentioned, in current implementation the range must be in one zone. > >So no I do not like this patch, it is not an improvement. >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me