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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 F2256C2BB48 for ; Tue, 15 Dec 2020 14:11:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C4C5B224D2 for ; Tue, 15 Dec 2020 14:11:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729374AbgLOOLO (ORCPT ); Tue, 15 Dec 2020 09:11:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728648AbgLOOKp (ORCPT ); Tue, 15 Dec 2020 09:10:45 -0500 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90A00C06179C for ; Tue, 15 Dec 2020 06:10:03 -0800 (PST) Received: by mail-ej1-x642.google.com with SMTP id 6so13248875ejz.5 for ; Tue, 15 Dec 2020 06:10:03 -0800 (PST) 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=NO1cdDn3rveUCdkxTy4K6Bz123za1ZPbmRLXpINNXFQ=; b=Cj5TDFrP2UXo3tmwVUdTH7+GGb5RV0uPmO3jFGipk9hla1suqNd371yVeP25Rb7d8R 95thK+Kh0JbtyxNnRkK1QRrqiZ6+aDvVemT0KoFkKgrhdDhdeIjuWDIIBY1fJxz/XCAD 5GZ+TCH1ctDULr82sPdO6oNK483aeK/vBbo5gKWwqupJhRnSgpppS20wv5YTPvbMj/Ks oeCMBtDzYPiSCngc2EEZ7N5Qv1l88T9Ndv4Df6mkbk9phQGuT+4qPHBxfWzfQG2sW5Ra ipaEaUl9qeKnOtRDEfXw3a1Y+gzWybJBjz8NjbwoO4TpGQhICs7CJx6+gWBEE/GzU6JV jk6A== 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=NO1cdDn3rveUCdkxTy4K6Bz123za1ZPbmRLXpINNXFQ=; b=GJ2yN/gQGgYktmnl3Ga2fh7AEqZ2WeBc+LC4zW6fTug+9rTTtX3Cne/YxOZEIOL1UG JEr8/C+jQ0wowoZaic/n9vG+/wP12z4yAcZAWksRSxDC7sG1/MzeDoaTgcuEeWdTXmrl HyZ4SSt9QUXIQxQLd/TOz39msMRGVqLHHjeVjxfejFMREdYjbO9n/AfwuXurX50sX5J/ 2GH7EoT0mA7cKojDcffQJASq9dpPMUtIgh//bKkwX1YwqZvOlcJzHaRweuQuLS6bv9wx +yVpMmzfpjoyit9wU9h7Eik0kZ6NoVisd4p4zt7PUqWMd2npZhjOihzWCxdWp5+YX5wY vU0g== X-Gm-Message-State: AOAM531wxsylSgT1zEfMqJf4j5oUJnv80aMP/rX2CtkWcHtXauIJVn5w 19z4tL57k1GubYWC5HUEcPBjhg== X-Google-Smtp-Source: ABdhPJzPRYE9A5cY1G5sZnG6cPGdS4cAxTTw3KczQzQ73+UAxRhdd0rjjZ9pos0m/8EZVDC0oufo1A== X-Received: by 2002:a17:906:8587:: with SMTP id v7mr26396217ejx.381.1608041402353; Tue, 15 Dec 2020 06:10:02 -0800 (PST) Received: from localhost ([2620:10d:c093:400::5:d6dd]) by smtp.gmail.com with ESMTPSA id d4sm19109737edq.36.2020.12.15.06.10.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Dec 2020 06:10:01 -0800 (PST) Date: Tue, 15 Dec 2020 15:07:54 +0100 From: Johannes Weiner To: Yang Shi Cc: guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com, david@fromorbit.com, mhocko@suse.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [v2 PATCH 2/9] mm: memcontrol: use shrinker_rwsem to protect shrinker_maps allocation Message-ID: <20201215140754.GD379720@cmpxchg.org> References: <20201214223722.232537-1-shy828301@gmail.com> <20201214223722.232537-3-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201214223722.232537-3-shy828301@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 14, 2020 at 02:37:15PM -0800, Yang Shi wrote: > Since memcg_shrinker_map_size just can be changd under holding shrinker_rwsem > exclusively, the read side can be protected by holding read lock, so it sounds > superfluous to have a dedicated mutex. This should not exacerbate the contention > to shrinker_rwsem since just one read side critical section is added. > > Signed-off-by: Yang Shi Acked-by: Johannes Weiner Thanks Yang, this is a step in the right direction. It would still be nice to also drop memcg_shrinker_map_size and (trivially) derive that value from shrinker_nr_max where necessary. It is duplicate state.