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=-2.5 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4CE41C41514 for ; Tue, 27 Aug 2019 12:09:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 18B45206BF for ; Tue, 27 Aug 2019 12:09:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18B45206BF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B5EBA6B0006; Tue, 27 Aug 2019 08:09:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B35566B000C; Tue, 27 Aug 2019 08:09:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A73806B000D; Tue, 27 Aug 2019 08:09:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0100.hostedemail.com [216.40.44.100]) by kanga.kvack.org (Postfix) with ESMTP id 885096B0006 for ; Tue, 27 Aug 2019 08:09:27 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 3CE884FE6 for ; Tue, 27 Aug 2019 12:09:27 +0000 (UTC) X-FDA: 75868087974.10.alley49_6f91ee2753335 X-HE-Tag: alley49_6f91ee2753335 X-Filterd-Recvd-Size: 3110 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Tue, 27 Aug 2019 12:09:26 +0000 (UTC) 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 284E9AF19; Tue, 27 Aug 2019 12:09:25 +0000 (UTC) Date: Tue, 27 Aug 2019 14:09:23 +0200 From: Michal Hocko To: Vlastimil Babka Cc: "Kirill A. Shutemov" , kirill.shutemov@linux.intel.com, Yang Shi , hannes@cmpxchg.org, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v2 PATCH -mm] mm: account deferred split THPs into MemAvailable Message-ID: <20190827120923.GB7538@dhcp22.suse.cz> References: <1566410125-66011-1-git-send-email-yang.shi@linux.alibaba.com> <20190822080434.GF12785@dhcp22.suse.cz> <20190822152934.w6ztolutdix6kbvc@box> <20190826074035.GD7538@dhcp22.suse.cz> <20190826131538.64twqx3yexmhp6nf@box> <20190827060139.GM7538@dhcp22.suse.cz> <20190827110210.lpe36umisqvvesoa@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 27-08-19 14:01:56, Vlastimil Babka wrote: > On 8/27/19 1:02 PM, Kirill A. Shutemov wrote: > > On Tue, Aug 27, 2019 at 08:01:39AM +0200, Michal Hocko wrote: > >> On Mon 26-08-19 16:15:38, Kirill A. Shutemov wrote: > >>> > >>> Unmapped completely pages will be freed with current code. Deferred split > >>> only applies to partly mapped THPs: at least on 4k of the THP is still > >>> mapped somewhere. > >> > >> Hmm, I am probably misreading the code but at least current Linus' tree > >> reads page_remove_rmap -> [page_remove_anon_compound_rmap ->\ deferred_split_huge_page even > >> for fully mapped THP. > > > > Well, you read correctly, but it was not intended. I screwed it up at some > > point. > > > > See the patch below. It should make it work as intened. > > > > It's not bug as such, but inefficientcy. We add page to the queue where > > it's not needed. > > But that adding to queue doesn't affect whether the page will be freed > immediately if there are no more partial mappings, right? I don't see > deferred_split_huge_page() pinning the page. > So your patch wouldn't make THPs freed immediately in cases where they > haven't been freed before immediately, it just fixes a minor > inefficiency with queue manipulation? Ohh, right. I can see that in free_transhuge_page now. So fully mapped THPs really do not matter and what I have considered an odd case is really happening more often. That being said this will not help at all for what Yang Shi is seeing and we need a more proactive deferred splitting as I've mentioned earlier. -- Michal Hocko SUSE Labs