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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT 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 85608C072B5 for ; Fri, 24 May 2019 17:06:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AF6821850 for ; Fri, 24 May 2019 17:06:50 +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="g/ueHChD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731828AbfEXRGq (ORCPT ); Fri, 24 May 2019 13:06:46 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:34083 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725886AbfEXRGq (ORCPT ); Fri, 24 May 2019 13:06:46 -0400 Received: by mail-pg1-f193.google.com with SMTP id h2so2330340pgg.1 for ; Fri, 24 May 2019 10:06:45 -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:user-agent; bh=Nd2Lj9Q7aDsjzQ8w/THzJxRiwvjWHcaNNXAaDuTseEo=; b=g/ueHChDmzv10RhToAZSHSTBKjmteHa2+GUrTouq4WT3zsId5XyPYsDLo0VEZ2lsk8 xxwdc+zYgqElB7Hvgr2sCKnjTYGslk7l0zl7pL6buSlo4cp3mxDXesT1bju4whIW9YTD Xuy4SOumA5cjyBIoyw9VlY9FgRNaGt/IqUr+XyQYlD5nDnja70C44raTby78ZUIDd1gl a5Sp9sBHrPzzyBHOEJQJe5yj3Kd+hIFzn2zlMyvZHtC4Byo12tj+FkG/59LC1tfn7w8G Pxe7hqzs2TKDKBOdg5W94Xk89woskg4bqexiagAxDpcv/zg5EhumBoaR1/Fa0bIqYdRx aAIQ== 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:user-agent; bh=Nd2Lj9Q7aDsjzQ8w/THzJxRiwvjWHcaNNXAaDuTseEo=; b=O5YQUjBgR2ElWFB9a5Dtx1Akp3OQNsOfxDnG7OsRXYXZhBUNt/jfv9M9H3Fhpxqx8Q yHNOy1Uonxlu8S+wB/cyxzN7jM5tbW1KoBinQ1YHzhZKtA8wGATmXYEbO28oPsVGVo3H nU/mHJ10Q+1qefmlMcq7F6waXHbbKlu/H0QShSvSF2kU+PW+DOM/Priser+7kvkPz9ej VtvbsIXLQL0PX29tT6xu+vcDvPwqARw2szJ70PzTwzRWW9FNnVvnIsxOc3Gm8WusKCCN aPtauVV9j5lOS/CvSuGNcE+gyuu3Qg9zJpRCVxKpiCEZFfUryFVQj5J6ML4/AY+UTVdi cP3Q== X-Gm-Message-State: APjAAAW9eKv6ur1nkfdvPrI3bjx49UPi4vjxZSimMe2L9S8jXsQr+Pfl 1gIUfzv7xStAEPPxSHJ75InyPg== X-Google-Smtp-Source: APXvYqyCulQRmI3PhrXkVMrT+R32nDK0uKlw4vnyyo1uY2kcnPUkhXPwQBLT45X7DGw97sr105YGzg== X-Received: by 2002:a17:90a:a616:: with SMTP id c22mr10749010pjq.46.1558717605295; Fri, 24 May 2019 10:06:45 -0700 (PDT) Received: from localhost ([2620:10d:c090:180::805]) by smtp.gmail.com with ESMTPSA id h5sm3485126pfk.163.2019.05.24.10.06.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 24 May 2019 10:06:44 -0700 (PDT) Date: Fri, 24 May 2019 13:06:42 -0400 From: Johannes Weiner To: Matthew Wilcox Cc: Shakeel Butt , Andrew Morton , Linux MM , linux-fsdevel , LKML , Kernel Team Subject: Re: xarray breaks thrashing detection and cgroup isolation Message-ID: <20190524170642.GA20546@cmpxchg.org> References: <20190523174349.GA10939@cmpxchg.org> <20190523183713.GA14517@bombadil.infradead.org> <20190523190032.GA7873@bombadil.infradead.org> <20190523192117.GA5723@cmpxchg.org> <20190523194130.GA4598@bombadil.infradead.org> <20190523195933.GA6404@cmpxchg.org> <20190524161146.GC1075@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190524161146.GC1075@bombadil.infradead.org> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, May 24, 2019 at 09:11:46AM -0700, Matthew Wilcox wrote: > On Thu, May 23, 2019 at 03:59:33PM -0400, Johannes Weiner wrote: > > My point is that we cannot have random drivers' internal data > > structures charge to and pin cgroups indefinitely just because they > > happen to do the modprobing or otherwise interact with the driver. > > > > It makes no sense in terms of performance or cgroup semantics. > > But according to Roman, you already have that problem with the page > cache. > https://lore.kernel.org/linux-mm/20190522222254.GA5700@castle/T/ > > So this argument doesn't make sense to me. You haven't addressed the rest of the argument though: why every user of the xarray, and data structures based on it, should incur the performance cost of charging memory to a cgroup, even when we have no interest in tracking those allocations on behalf of a cgroup. Which brings me to repeating the semantics argument: it doesn't make sense to charge e.g. driver memory, which is arguably a shared system resource, to whoever cgroup happens to do the modprobe / ioctl etc. Anyway, this seems like a fairly serious regression, and it would make sense to find a self-contained, backportable fix instead of something that has subtle implications for every user of the xarray / ida code.