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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 78080C4363D for ; Fri, 2 Oct 2020 10:03:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1DF8D206DD for ; Fri, 2 Oct 2020 10:03:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="EO4uUzWS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387682AbgJBKDy (ORCPT ); Fri, 2 Oct 2020 06:03:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:36300 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725993AbgJBKDx (ORCPT ); Fri, 2 Oct 2020 06:03:53 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1601633032; 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: in-reply-to:in-reply-to:references:references; bh=xShwnns1sZmu50F4PGsDB78YoAb2/a84doWxwWdQAao=; b=EO4uUzWSbENtuiq0XnbdzwUPSfuTzfNHcZI8XZJjRguG48J0SrZxcdQiLcStNq9QTdKUGY 8S2T1NBlmqqWHSFC4s1DKW6giHm8i0xtJlmeLXVPK8bB8vNZx+I4f5HNJUu+hKxXAIRugf OXCcD4zK1aMsofHcbmD4kr4n6lmBuOw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 352C1AC2B; Fri, 2 Oct 2020 10:03:52 +0000 (UTC) Date: Fri, 2 Oct 2020 12:03:50 +0200 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Johannes Weiner Cc: Roman Gushchin , Andrew Morton , Shakeel Butt , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com Subject: Re: [PATCH v4 4/4] mm: convert page kmemcg type to a page memcg flag Message-ID: <20201002100350.GC24008@blackbody.suse.cz> References: <20201001002710.748166-1-guro@fb.com> <20201001002710.748166-5-guro@fb.com> <20201001170036.GA29848@blackbook> <20201001172713.GA500308@cmpxchg.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="MnLPg7ZWsaic7Fhd" Content-Disposition: inline In-Reply-To: <20201001172713.GA500308@cmpxchg.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --MnLPg7ZWsaic7Fhd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Oct 01, 2020 at 01:27:13PM -0400, Johannes Weiner wrote: > The activation code is the only path where page migration is not > excluded. Because unlike with page state statistics, we don't really > mind a race when counting an activation event. Thanks for the explanation. I see why the accessor trio is justified. > I do think there is a bug, though: mem_cgroup_move_account() should > use WRITE_ONCE() on page->mem_cgroup. If this were a bug, wouldn't be the proper approach rcu_assign_pointer()/rcu_dereference() pair? Michal --MnLPg7ZWsaic7Fhd Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEEoQaUCWq8F2Id1tNia1+riC5qSgFAl92+wMACgkQia1+riC5 qSjoXBAAijzh02/9TXGICO7j+GMJCp6nN4wR6sLgCwSepvipg9XWa14yJiDqRzy1 hHVRStm2iKcS3jGsCWsz0qvE+k9CDosua5asddxwfQXWggJszaTzkrTEkBIj/iIW jFR8sMzmgfHSIo+m93FvRT/QHoZC1s4+J/PauBwvUwCLN0kB6/V964HIbt+m6zKO xAzczqa6H/JMFPovVu6gGguT8dZqA847COfuD3+J8ZkK3ZUTu74epXEAjJarkokQ ibkZwuEVOzqoB3CuCugb2dO0W6bqcFXqZw6T4V1FG54QwpoBiq9/kGcG7Z3djIr2 15kRQIbE7JqtLJQMYD+oXbLpKoUUXXZkuhUNWh8ozrX5m4kBeXkIeOpCEZlHqYrH Mc8ydvwx+Ajy0oofmDqqNKd8aV/9bBAVQpqxsZD/fRjIzkaT20HQnTMtK6UgnsH4 2gw5NCGv0EiCEBhpdWIlwFoaNMOinYeZwr+nPVK4WZLSyZZyPcBFdIW+7O7WkfPK n39mmmngFevD/EP2iCyC8hhZ6Uht+qVeVHVpHKvE82NgrDfUSuhoKbJBNoYQrIV3 57MLMrP/RACcxU/3D06asMPg08k36b3yV5TuSDcu3E/PlLpZnwlQEblws8+120/k xKEnW1XoA2zRaOB1ojkNy+YcyBOlmdPFMRjAgKffEc4U6wZbNcw= =Qjsf -----END PGP SIGNATURE----- --MnLPg7ZWsaic7Fhd--