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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C8D8C433EF for ; Wed, 6 Apr 2022 01:08:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6A28A6B0073; Tue, 5 Apr 2022 21:08:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6797B6B0074; Tue, 5 Apr 2022 21:08:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4F4376B0075; Tue, 5 Apr 2022 21:08:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0019.hostedemail.com [216.40.44.19]) by kanga.kvack.org (Postfix) with ESMTP id 3F4E76B0073 for ; Tue, 5 Apr 2022 21:08:13 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id EA42C8249980 for ; Wed, 6 Apr 2022 01:08:02 +0000 (UTC) X-FDA: 79324667646.26.AA86B01 Received: from mail-il1-f177.google.com (mail-il1-f177.google.com [209.85.166.177]) by imf23.hostedemail.com (Postfix) with ESMTP id 74A9B140034 for ; Wed, 6 Apr 2022 01:08:02 +0000 (UTC) Received: by mail-il1-f177.google.com with SMTP id x9so871746ilc.3 for ; Tue, 05 Apr 2022 18:08:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RgvBhB60r34bKOm2tCGx0FLu0SdJzIYZfN+oE6mYW4Y=; b=UCNyZ54P2mgXYG0SUsGZv0scK1xaO99fPJQNVGaOcBBfVEqjvQWJbhpUIt9gU/3XWy i1AIqrFuz6OljshjkJ4io2XcByq5P5phDtENYPHWUiAXdmExOJbEGf4bnIsPloqvrSVp gfVTsJ6ugbeqHqj8t+OgchC3cON2X9yJ4tb8TPAbmr5MyrtpuZFB8QOzD9zlxC7nWjRd 0djc5eUqkeqQREev7dlWuZK7CObjNQPhXfsRPHPVaMTGnFug9sCPmEJQgAMVooK/KPYU auxh5Czx04A5jkdZ/uXqiokinos3NqmfNX1n5/a/CgMMMmh4nQvDTOvQxE4YeRMHkAaZ uFdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RgvBhB60r34bKOm2tCGx0FLu0SdJzIYZfN+oE6mYW4Y=; b=3ffxTyV1OKqn9giFrrJdvOLBajT9LMXLD2nC2mZWFEwDFLP7W6J8NCP+T42GeLWcyU 5aafUI9PGyJwv3HAO6HRP0Xq3+m+IBAHXCXsnRjV4CmKDERlXf1seTVkNFbvPQWisQkX rhQU+4GZ2+xxaYZI7FTRnneSx2KbhhPIez6MxmCLMjRAZ1DijFyZYBPJ/tvjtEW6vpG+ G685/Ty7SSR4WYAlJKgUEZi2qWLsvrEDTzKM7QJpjqnhoFPi55m3EdKtBsggBuwM4OmL x5u1WhQwEkJ2ihJssf++db00ZXo27J5Sjo9T24izIP/8rM4YFMJvtdGRT88RxdSmpLTE o3vw== X-Gm-Message-State: AOAM5315bHQnPqRxTDsE0WQ3+SBx4q/Gc7LWIauPj4cvoSqN4ieK2/Ti 13nTHSgum3Asc3Wa2MZPINvA7wKEy3oSLvsv7G6DIA== X-Google-Smtp-Source: ABdhPJxq3KHZ1VgC8H6k/nkG/PU0tBmZKSI4Zq/E9uh0ebH59q9hVWU4W+VT5mcgO2wHoffP8694DLo9F8gK5lolIXQ= X-Received: by 2002:a92:cd8b:0:b0:2c9:ded9:f20d with SMTP id r11-20020a92cd8b000000b002c9ded9f20dmr2825689ilb.300.1649207280627; Tue, 05 Apr 2022 18:08:00 -0700 (PDT) MIME-Version: 1.0 References: <20220331084151.2600229-1-yosryahmed@google.com> <87y20nzyw4.fsf@yhuang6-desk2.ccr.corp.intel.com> <87o81fujdc.fsf@yhuang6-desk2.ccr.corp.intel.com> In-Reply-To: <87o81fujdc.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Wei Xu Date: Tue, 5 Apr 2022 18:07:49 -0700 Message-ID: Subject: Re: [PATCH resend] memcg: introduce per-memcg reclaim interface To: "Huang, Ying" Cc: Michal Hocko , Yosry Ahmed , Johannes Weiner , Shakeel Butt , Andrew Morton , David Rientjes , Tejun Heo , Zefan Li , Roman Gushchin , Cgroups , "open list:DOCUMENTATION" , Linux Kernel Mailing List , Linux MM , Jonathan Corbet , Yu Zhao , Dave Hansen , Greg Thelen Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 74A9B140034 X-Stat-Signature: x8nbp4hghbqoytu81tb3hkwpqrexchip X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=UCNyZ54P; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf23.hostedemail.com: domain of weixugc@google.com designates 209.85.166.177 as permitted sender) smtp.mailfrom=weixugc@google.com X-HE-Tag: 1649207282-534728 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 Tue, Apr 5, 2022 at 5:49 PM Huang, Ying wrote: > > Wei Xu writes: > > > On Sat, Apr 2, 2022 at 1:13 AM Huang, Ying wrote: > >> > >> Wei Xu writes: > >> > >> > On Fri, Apr 1, 2022 at 6:54 AM Michal Hocko wrote: > >> >> > >> >> On Thu 31-03-22 08:41:51, Yosry Ahmed wrote: > >> >> > From: Shakeel Butt > >> >> > > >> > >> [snip] > >> > >> >> > Possible Extensions: > >> >> > -------------------- > >> >> > > >> >> > - This interface can be extended with an additional parameter or flags > >> >> > to allow specifying one or more types of memory to reclaim from (e.g. > >> >> > file, anon, ..). > >> >> > > >> >> > - The interface can also be extended with a node mask to reclaim from > >> >> > specific nodes. This has use cases for reclaim-based demotion in memory > >> >> > tiering systens. > >> >> > > >> >> > - A similar per-node interface can also be added to support proactive > >> >> > reclaim and reclaim-based demotion in systems without memcg. > >> >> > > >> >> > For now, let's keep things simple by adding the basic functionality. > >> >> > >> >> Yes, I am for the simplicity and this really looks like a bare minumum > >> >> interface. But it is not really clear who do you want to add flags on > >> >> top of it? > >> >> > >> >> I am not really sure we really need a node aware interface for memcg. > >> >> The global reclaim interface will likely need a different node because > >> >> we do not want to make this CONFIG_MEMCG constrained. > >> > > >> > A nodemask argument for memory.reclaim can be useful for memory > >> > tiering between NUMA nodes with different performance. Similar to > >> > proactive reclaim, it can allow a userspace daemon to drive > >> > memcg-based proactive demotion via the reclaim-based demotion > >> > mechanism in the kernel. > >> > >> I am not sure whether nodemask is a good way for demoting pages between > >> different types of memory. For example, for a system with DRAM and > >> PMEM, if specifying DRAM node in nodemask means demoting to PMEM, what > >> is the meaning of specifying PMEM node? reclaiming to disk? > >> > >> In general, I have no objection to the idea in general. But we should > >> have a clear and consistent interface. Per my understanding the default > >> memcg interface is for memory, regardless of memory types. The memory > >> reclaiming means reduce the memory usage, regardless of memory types. > >> We need to either extending the semantics of memory reclaiming (to > >> include memory demoting too), or add another interface for memory > >> demoting. > > > > Good point. With the "demote pages during reclaim" patch series, > > reclaim is already extended to demote pages as well. For example, > > can_reclaim_anon_pages() returns true if demotion is allowed and > > shrink_page_list() can demote pages instead of reclaiming pages. > > These are in-kernel implementation, not the ABI. So we still have > the opportunity to define the ABI now. > > > Currently, demotion is disabled for memcg reclaim, which I think can > > be relaxed and also necessary for memcg-based proactive demotion. I'd > > like to suggest that we extend the semantics of memory.reclaim to > > cover memory demotion as well. A flag can be used to enable/disable > > the demotion behavior. > > If so, > > # echo A > memory.reclaim > > means > > a) "A" bytes memory are freed from the memcg, regardless demoting is > used or not. > > or > > b) "A" bytes memory are reclaimed from the memcg, some of them may be > freed, some of them may be just demoted from DRAM to PMEM. The total > number is "A". > > For me, a) looks more reasonable. > We can use a DEMOTE flag to control the demotion behavior for memory.reclaim. If the flag is not set (the default), then no_demotion of scan_control can be set to 1, similar to reclaim_pages(). The question is then whether we want to rename memory.reclaim to something more general. I think this name is fine if reclaim-based demotion is an accepted concept.