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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 366E3C4363A for ; Tue, 27 Oct 2020 07:05:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E612521556 for ; Tue, 27 Oct 2020 07:05:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SxaK+ZeI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2507280AbgJ0HFg (ORCPT ); Tue, 27 Oct 2020 03:05:36 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:52868 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390236AbgJ0HFg (ORCPT ); Tue, 27 Oct 2020 03:05:36 -0400 Received: by mail-wm1-f65.google.com with SMTP id c194so302386wme.2 for ; Tue, 27 Oct 2020 00:05:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=cc:subject:to:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=0Uzi3RvXZDdd/vEOArqhL4/rMcsMRvXi+9GkyM30so8=; b=SxaK+ZeInnKzLmeGOydI0kt9GYmAFn9l50XfKN+oxTu55BDjv3edWvMsth1f5NXIJs Q1bQXDygcn6a1RKmVmgOI8OBBfi40qQXII5EtuJZFzB1XZrB5maBMpz3KENJdcjsWe8t NwD/G6gZGd1jgnayBnJuFVYMcbzIB7QqxgblsFzxTpWSiDf9tnLo18msOKjX2viaa1K1 VxWU7Cc8XtZDrLF5X4rM+uMTubw1iP8fgKkEWLdwovgXPMLcAJKxYD6RFXBe96eMtBbK Kk0ApbKkGamaeB3YQ2h08wi/GMpnQ5iyIx5/rP7JfSD49LoIPLNYKhcNcKGK/Y3JzAgT PUUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:cc:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=0Uzi3RvXZDdd/vEOArqhL4/rMcsMRvXi+9GkyM30so8=; b=ovHoim3mR2s7s2EQw/K9f+yf0DZexwfW5iQv6ofX9V4BUpmREJSIwQNDR0DXTzsfBA WYyWGU1jAVisFlVUgjuIKZMNPT0Ub4mouCf7nt4LgnR1GMGKTeWnV29gvtDZ1vjhWHku e3YZsqeJAuHlwARdqeZ9//O2YcBYSO9msarM6P8DnD5dKvtjY16mCFZp+5Bapl1Ct/k7 ilQewxq3uLX8UxH/f3U+nKP7LqEgPu8d0u4TSfcA/wRJgXJmLn6hKYz8QdCOVj6U+3g4 ZUlvtJH1m+HefvT5Ljh/iq9Kccr+zwCa6Fsw2vy8ZZRfogUMSFGuAB76OGYHmAsEfGv9 C9+Q== X-Gm-Message-State: AOAM530aiGnlHPZY+4ul/YoUA3u7Yrst4IAO/DZWNtpe521I8kPPib+p grxuNJj/54BkJvP93KEw7II= X-Google-Smtp-Source: ABdhPJwjBGvn6y57kqTcEM6MKExa+3rO1678y48C5X9yLu++T6iR3qbIGJ7GEqTTN7cExri1njk9ow== X-Received: by 2002:a1c:cc07:: with SMTP id h7mr1078946wmb.55.1603782334422; Tue, 27 Oct 2020 00:05:34 -0700 (PDT) Received: from ?IPv6:2001:a61:245a:d801:2e74:88ad:ef9:5218? ([2001:a61:245a:d801:2e74:88ad:ef9:5218]) by smtp.gmail.com with ESMTPSA id y2sm823787wrh.0.2020.10.27.00.05.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Oct 2020 00:05:33 -0700 (PDT) Cc: mtk.manpages@gmail.com, linux-man , Linux-MM , Mark Mossberg Subject: Re: [PATCH] proc.5: Document inaccurate RSS due to SPLIT_RSS_COUNTING To: Jann Horn References: <20201012114940.1317510-1-jannh@google.com> From: "Michael Kerrisk (man-pages)" Message-ID: <0a090c14-6b70-4284-bb2d-4fbfd1146aaf@gmail.com> Date: Tue, 27 Oct 2020 08:05:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org Hi Jann, On 10/12/20 4:52 PM, Jann Horn wrote: > On Mon, Oct 12, 2020 at 1:49 PM Jann Horn wrote: >> Since 34e55232e59f7b19050267a05ff1226e5cd122a5 (introduced back in >> v2.6.34), Linux uses per-thread RSS counters to reduce cache contention on >> the per-mm counters. With a 4K page size, that means that you can end up >> with the counters off by up to 252KiB per thread. > > Actually, as Mark Mossberg pointed out to me off-thread, the counters > can actually be off by many times more... So, does your patch to proc.5 need tweaking, or can I just apply as is? Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/