From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id 9FD4A6B0003 for ; Fri, 23 Feb 2018 11:34:22 -0500 (EST) Received: by mail-it0-f71.google.com with SMTP id p11so2720685itc.5 for ; Fri, 23 Feb 2018 08:34:22 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id v8sor759046itv.115.2018.02.23.08.34.21 for (Google Transport Security); Fri, 23 Feb 2018 08:34:21 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20180223081147.GD30773@dhcp22.suse.cz> References: <20180205220325.197241-1-dancol@google.com> <20180222001635.GB27147@rodete-desktop-imager.corp.google.com> <20180222020633.GC27147@rodete-desktop-imager.corp.google.com> <20180223081147.GD30773@dhcp22.suse.cz> From: Daniel Colascione Date: Fri, 23 Feb 2018 08:34:19 -0800 Message-ID: Subject: Re: [PATCH] Synchronize task mm counters on context switch Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Minchan Kim , linux-mm@kvack.org, Andrew Morton , Oleg Nesterov , Peter Zijlstra On Fri, Feb 23, 2018 at 12:11 AM, Michal Hocko wrote: > On Wed 21-02-18 18:49:35, Daniel Colascione wrote: > [...] >> For more context: on Android, we've historically scanned each processes's >> address space using /proc/pid/smaps (and /proc/pid/smaps_rollup more >> recently) to extract memory management statistics. We're looking at >> replacing this mechanism with the new /proc/pid/status per-memory-type >> (e.g., anonymous, file-backed) counters so that we can be even more >> efficient, but we'd like the counts we collect to be accurate. > > If you need the accuracy then why don't you simply make > SPLIT_RSS_COUNTING configurable and disable it in your setup? I considered that option, but it feels like a last resort. I think agreement between /proc/pid/status and /proc/pid/smaps is a correctness issue, and I'd prefer to fix the correctness issue globally. That said, *deleting* the SPLIT_RSS_COUNTING code would be nice and simple. How sure are we that the per-task accounting is really needed? Maybe I'm wrong, but I feel like taking page faults will touch per-mm data structures anyway, so one additional atomic update on the mm shouldn't hurt all that much. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org