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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA38DC433F5 for ; Mon, 31 Jan 2022 17:25:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 72E338D0016; Mon, 31 Jan 2022 12:25:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6DEF88D0001; Mon, 31 Jan 2022 12:25:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5A6A88D0016; Mon, 31 Jan 2022 12:25:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0220.hostedemail.com [216.40.44.220]) by kanga.kvack.org (Postfix) with ESMTP id 4BA6A8D0001 for ; Mon, 31 Jan 2022 12:25:16 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 098FC827F308 for ; Mon, 31 Jan 2022 17:25:16 +0000 (UTC) X-FDA: 79091258232.22.8195CD3 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 89F5720004 for ; Mon, 31 Jan 2022 17:25:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643649915; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PaMPeaT7bqTywU/6EXOdBYInz5ZUKSgh51n5zqNu8us=; b=fqYO0qoWf45lgm9m+GeZO6rFuZuzYqHSGJb3fZKnAbKRwfV+tvDZ393dh/yNiHPQYrX9sI 1tASqgF8SV5Hx4+dZAzG9vtJ1iw3QnqnE0gyxKk/UiiptoLBIIHJz9rSFFws/dIUrSy4x6 sd8oJNiwvPqAckhH8t25rTcbMxHbBf0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-558-WevAcsvfPmSx_CbH-QId1w-1; Mon, 31 Jan 2022 12:25:09 -0500 X-MC-Unique: WevAcsvfPmSx_CbH-QId1w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3450793921; Mon, 31 Jan 2022 17:25:07 +0000 (UTC) Received: from [10.22.16.244] (unknown [10.22.16.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id BD20F6E202; Mon, 31 Jan 2022 17:25:05 +0000 (UTC) Message-ID: <9abc9cb8-8734-90b0-c495-8df89c7bb579@redhat.com> Date: Mon, 31 Jan 2022 12:25:05 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH 1/3] mm, memcg: Don't put offlined memcg into local stock Content-Language: en-US To: Roman Gushchin Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Vlastimil Babka , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Muchun Song References: <20211001190938.14050-1-longman@redhat.com> <20211001190938.14050-2-longman@redhat.com> <95ba1931-e9c9-45c3-b080-d28f2ad368a7@redhat.com> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Rspamd-Queue-Id: 89F5720004 X-Rspam-User: nil Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=fqYO0qoW; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf13.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=longman@redhat.com X-Stat-Signature: 1i14g5irt9zfckhhr4b5u1p7dwjr3yu1 X-Rspamd-Server: rspam08 X-HE-Tag: 1643649915-720357 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 1/31/22 12:19, Roman Gushchin wrote: > On Mon, Jan 31, 2022 at 12:15:19PM -0500, Waiman Long wrote: >> On 1/31/22 12:09, Waiman Long wrote: >>> On 1/31/22 12:01, Roman Gushchin wrote: >>>> On Sun, Jan 30, 2022 at 10:55:56PM -0500, Waiman Long wrote: >>>>> On 10/1/21 19:51, Roman Gushchin wrote: >>>>>> On Fri, Oct 01, 2021 at 03:09:36PM -0400, Waiman Long wrote: >>>>>>> When freeing a page associated with an offlined memcg, refill_stock() >>>>>>> will put it into local stock delaying its demise until another memcg >>>>>>> comes in to take its place in the stock. To avoid that, we now check >>>>>>> for offlined memcg and go directly in this case to the slowpath for >>>>>>> the uncharge via the repurposed cancel_charge() function. >>>>>> Hi Waiman! >>>>>> >>>>>> I'm afraid it can make a cleanup of a dying cgroup slower: for every >>>>>> released page we'll potentially traverse the whole cgroup tree and >>>>>> decrease atomic page counters. >>>>>> >>>>>> I'm not sure I understand the benefits we get from this change which >>>>>> do justify the slowdown on the cleanup path. >>>>>> >>>>>> Thanks! >>>>> I was notified of a lockdep splat that this patch may help to prevent. >>>> Would you mind to test this patch: >>>> https://www.spinics.net/lists/cgroups/msg31244.html ? >>>> >>>> It should address this dependency. >>> Thanks for the pointer. I believe that your patch should be able to >>> address this circular locking dependency. >>> >>> Feel free to add my >>> >>> Reviewed-by: Waiman Long >> BTW, have you posted it to lkml? If not, would you mind doing so? > Not yet. > > I was waiting for Alexander to confirm that it resolves the originally reported > issue. I just pinged him, will wait for tomorrow and post the patch in any case. > > Thanks! I see. This is not a problem that is easily reproducible. You need to hit the right timing for the lockdep splat to appear. Regards, Longman