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=-13.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 37C18C433DB for ; Thu, 28 Jan 2021 14:06:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8A2564DD9 for ; Thu, 28 Jan 2021 14:06:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231263AbhA1OGK (ORCPT ); Thu, 28 Jan 2021 09:06:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229840AbhA1OGF (ORCPT ); Thu, 28 Jan 2021 09:06:05 -0500 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA328C061573 for ; Thu, 28 Jan 2021 06:05:24 -0800 (PST) Received: by mail-lj1-x22c.google.com with SMTP id s18so6445750ljg.7 for ; Thu, 28 Jan 2021 06:05:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=y3gG47U5h6Z0ms3PRQUM8QBx0aKm7Kdbts1+blceg04=; b=CfsrBQTGs0Esbt43WsOC7Vky4axjxTddmdc93F7OYhDFG0xRi8EFPzo+ljigoe2pot nl08e50onWdGXMFNApzFBAnmpeofi5yYUDo1CTz9cqW42zyNQd9HH0L/9STRoEjZ5zJc fTQNEKQF+kRCuFHnyz08L6kuBS11UhljPl/rF/qd+Dep7b9BbEiHXcPCIznldnx2v/az YhUiFaD5ezD3+239rpnSr1++mcg29oPu7pI5YQLwKfPBN7dvfoXrUj0cu4J0tiwMoTNG iQABFGbqct02pstWAwbScdjSu0GGO2jqtYNWDU9LQ7vjkegvI5234iUqZC4wfqsWXuRJ Fycg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=y3gG47U5h6Z0ms3PRQUM8QBx0aKm7Kdbts1+blceg04=; b=oWorp6iLvDuD+hr5DLQXrbHHzvUudo5nLcG1m9ya05TG0oCW7ENWCGX6OKS95+Y9L0 L01Z+DjClldXoHiRZ3SWpcDMVHArgZoyFmR9JBhxRebtTzC/wgMpp+K/yDDtVu4nuFY5 +NtXjPt0bQu4U+U0rKJjM/DaKwjMIPDf31rKjg9o16cdp10wbU1g6EgPWKQAqHh4UPdA ty6M8vWsgBoY2Kn7RzDAXRtjb2DMgB+BJwSFpjxcNyqkqL+Ztp5jUOhBkc+dDNQnpqNS 8L7QMm0Q8ZNMLwiN9NlbHbZy3IclSm/lWR8kzu7WmZy793W3O4/yDyt668ct4ffF+pTZ w8Gg== X-Gm-Message-State: AOAM533OHHZTj4qv+KeX/ZvqVmNpkr3m4N6bREzfogNUIWDyw+P0Iygz MK5J62aTyeU9MakVzO4kyT+faL5QNpNTtaG12Bhgqg== X-Google-Smtp-Source: ABdhPJzmRLfShao52Wl8c2GnOI8Esxdu0gDu7Q4WjHT9JBMYe6CY6I8ohfbMaBXYGGmZSWG03007q03WUtavSFPY58o= X-Received: by 2002:a2e:9ed1:: with SMTP id h17mr8071290ljk.160.1611842723157; Thu, 28 Jan 2021 06:05:23 -0800 (PST) MIME-Version: 1.0 References: <20210121122723.3446-1-rppt@kernel.org> <20210121122723.3446-9-rppt@kernel.org> <20210125165451.GT827@dhcp22.suse.cz> <20210125213817.GM6332@kernel.org> <20210126144838.GL308988@casper.infradead.org> <20210126150555.GU827@dhcp22.suse.cz> <20210127184213.GA919963@carbon.dhcp.thefacebook.com> In-Reply-To: From: Shakeel Butt Date: Thu, 28 Jan 2021 06:05:11 -0800 Message-ID: Subject: Re: [PATCH v16 08/11] secretmem: add memcg accounting To: Michal Hocko Cc: Roman Gushchin , Matthew Wilcox , Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , David Hildenbrand , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel , Linux MM , LKML , linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Jan 27, 2021 at 11:59 PM Michal Hocko wrote: > > On Wed 27-01-21 10:42:13, Roman Gushchin wrote: > > On Tue, Jan 26, 2021 at 04:05:55PM +0100, Michal Hocko wrote: > > > On Tue 26-01-21 14:48:38, Matthew Wilcox wrote: > > > > On Mon, Jan 25, 2021 at 11:38:17PM +0200, Mike Rapoport wrote: > > > > > I cannot use __GFP_ACCOUNT because cma_alloc() does not use gfp. > > > > > Besides, kmem accounting with __GFP_ACCOUNT does not seem > > > > > to update stats and there was an explicit request for statistics: > > > > > > > > > > https://lore.kernel.org/lkml/CALo0P13aq3GsONnZrksZNU9RtfhMsZXGWhK1n=xYJWQizCd4Zw@mail.gmail.com/ > > > > > > > > > > As for (ab)using NR_SLAB_UNRECLAIMABLE_B, as it was already discussed here: > > > > > > > > > > https://lore.kernel.org/lkml/20201129172625.GD557259@kernel.org/ > > > > > > > > > > I think that a dedicated stats counter would be too much at the moment and > > > > > NR_SLAB_UNRECLAIMABLE_B is the only explicit stat for unreclaimable memory. > > > > > > > > That's not true -- Mlocked is also unreclaimable. And doesn't this > > > > feel more like mlocked memory than unreclaimable slab? It's also > > > > Unevictable, so could be counted there instead. > > > > > > yes, that is indeed true, except the unreclaimable counter is tracking > > > the unevictable LRUs. These pages are not on any LRU and that can cause > > > some confusion. Maybe they shouldn't be so special and they should live > > > on unevistable LRU and get their stats automagically. > > > > > > I definitely do agree that this would be a better fit than NR_SLAB > > > abuse. But considering that this is somehow even more special than mlock > > > then a dedicated counter sounds as even better fit. > > > > I think it depends on how large these areas will be in practice. > > If they will be measured in single or double digits MBs, a separate entry > > is hardly a good choice: because of the batching the displayed value > > will be in the noise range, plus every new vmstat item adds to the > > struct mem_cgroup size. > > > > If it will be measured in GBs, of course, a separate counter is preferred. > > So I'd suggest to go with NR_SLAB (which should have been named NR_KMEM) > > as now and conditionally switch to a separate counter later. > > I really do not think the overall usage matters when it comes to abusing > other counters. Changing this in future will be always tricky and there > always be our favorite "Can this break userspace" question. Yes we dared > to change meaning of some counters but this is not generally possible. > Just have a look how accounting shmem as a page cache has turned out > being much more tricky than many like. > > Really if a separate counter is a big deal, for which I do not see any > big reason, then this should be accounted as unevictable (as suggested > by Matthew) and ideally pages of those mappings should be sitting in the > unevictable LRU as well unless there is a strong reason against. > Why not decide based on the movability of these pages? If movable then unevictable LRU seems like the right way otherwise NR_SLAB.