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=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS 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 4A3D0C43331 for ; Thu, 2 Apr 2020 15:18:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 08C7C2072E for ; Thu, 2 Apr 2020 15:18:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="L/SnQjBf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 08C7C2072E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=cmpxchg.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9497C8E0009; Thu, 2 Apr 2020 11:18:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 902FD8E0007; Thu, 2 Apr 2020 11:18:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7E8BE8E0009; Thu, 2 Apr 2020 11:18:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0113.hostedemail.com [216.40.44.113]) by kanga.kvack.org (Postfix) with ESMTP id 64F068E0007 for ; Thu, 2 Apr 2020 11:18:55 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1094D8248047 for ; Thu, 2 Apr 2020 15:18:55 +0000 (UTC) X-FDA: 76663272630.25.beds56_6aec58a1ec330 X-HE-Tag: beds56_6aec58a1ec330 X-Filterd-Recvd-Size: 3799 Received: from mail-qv1-f65.google.com (mail-qv1-f65.google.com [209.85.219.65]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Apr 2020 15:18:54 +0000 (UTC) Received: by mail-qv1-f65.google.com with SMTP id z13so1843832qvw.3 for ; Thu, 02 Apr 2020 08:18:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=X4md8GfFb/AZLlmWivRcEwSCP4uBimc7oKbXY4Cuzbs=; b=L/SnQjBfnp5fEn4nBLMR6OIrZCUsqaFG32VM3D8P0P8Lj/uoYnjkRyEnuYvXsJsAKt c4igzrWSnvwBSj3E7mr0QbuhFJhboCmmv66EkfRKM8dykWur9UCs7QjwYmhFzRp4O+A4 SnrLBfG8ir/Oio7mvh4OgFCEi2cahY9VIyMpFSkHRdm41lB0/v0GSq1mKWVd2TiCyBlN hI6cIgvd6bBViEDgjTfBgb3PQnim/I28LCR10Uk8FN4kj7u9VdBwqKzsszZNJndU/ap/ B/jD43fEcMR1E7yUPLdB4B9rCGNhvxza6rn5dvPkZt/C61cv9D6z0rzi3GwPV+Lp5T9D VM4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=X4md8GfFb/AZLlmWivRcEwSCP4uBimc7oKbXY4Cuzbs=; b=QhQZEn/IugWvgYmZpVunUEHnlxsyaZtarSrY4nQSG3BIXXFX7KNGVs3kgTTQ7GgdRd kN0e4Vn3WHz9YUbhDO+8Lqyx9lGTMw4ydnCFZgHl0YRNPzfVWz8tNteJaM0HpGSKGeF8 WSOtCbL99a5XHFGO8pTZLy9j24PBvhV2vXD7i32/pxHceNc+QhOh4Vr5AwZM/jIGW+ZY hXmZlZBW/fS6xlsCCjH0/FktBU4wE5N4V1MCmrYSuOmlPvBfW0fFOxZ5z3f0qulD3H0a 5dbyvekymeYYtC59UY3MxhYiHzbL6oW/wKu41yHlCX4CGAS27vLbOwscol6J8qBAzstW +xmw== X-Gm-Message-State: AGi0PuZd8dz0ypAzK2Fnjr2d3rDK93dXvB6dleCwB2n01TFyoJd1yBho fEPuZej1lj0np52SpQIHnjoiXQ== X-Google-Smtp-Source: APiQypL5Dn4DcQmenazeGPmJARieWyi3C0ntxFpd4l0Ao5mKkYmQaN0AZVEOfdy/PupIGM0JUmOwRg== X-Received: by 2002:ad4:55cd:: with SMTP id bt13mr3597389qvb.111.1585840733984; Thu, 02 Apr 2020 08:18:53 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::11c9]) by smtp.gmail.com with ESMTPSA id z66sm3721863qkb.94.2020.04.02.08.18.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2020 08:18:53 -0700 (PDT) Date: Thu, 2 Apr 2020 11:18:52 -0400 From: Johannes Weiner To: Chris Down Cc: Andrew Morton , Tejun Heo , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] mm, memcg: Bypass high reclaim iteration for cgroup hierarchy root Message-ID: <20200402151852.GD2089@cmpxchg.org> References: <20200312164137.GA1753625@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200312164137.GA1753625@chrisdown.name> 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 Thu, Mar 12, 2020 at 04:41:37PM +0000, Chris Down wrote: > The root of the hierarchy cannot have high set, so we will never reclaim > based on it. This makes that clearer and avoids another entry. > > Signed-off-by: Chris Down > Cc: Andrew Morton > Cc: Johannes Weiner > Cc: Tejun Heo > Cc: linux-mm@kvack.org > Cc: cgroups@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@fb.com This makes sense, memory.high doesn't exist on the root. And the mem_cgroup_is_root() check, a simple pointer comparison, is cheaper than reading the page_counter atomic and memcg->high (which we already know to be PAGE_COUNTER_MAX). Acked-by: Johannes Weiner