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 530C5C433F5 for ; Tue, 26 Apr 2022 07:00:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E0E366B0078; Tue, 26 Apr 2022 03:00:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D943E6B007B; Tue, 26 Apr 2022 03:00:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C36196B007E; Tue, 26 Apr 2022 03:00:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id B15F66B0078 for ; Tue, 26 Apr 2022 03:00:15 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 9048C255E9 for ; Tue, 26 Apr 2022 07:00:15 +0000 (UTC) X-FDA: 79398131190.25.B654070 Received: from mail-ua1-f48.google.com (mail-ua1-f48.google.com [209.85.222.48]) by imf11.hostedemail.com (Postfix) with ESMTP id 67F1E40047 for ; Tue, 26 Apr 2022 07:00:12 +0000 (UTC) Received: by mail-ua1-f48.google.com with SMTP id g22so6522122uam.12 for ; Tue, 26 Apr 2022 00:00:14 -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=YiJEB0dRG8Vs28wunrpsUd3aNm5kWfCeFbd3eFY3as0=; b=d5Yk9vkBLEnKHZ514Yf7ffIGn1EMaNSf9hcUKn32e7vRywUbt99pLhvqkR7Liz+aP8 sozJ0ZzYbXQ8jrjtb5NyDXRaai+A2UT7dybpsV4vswDl9pVDBXrK/HvM3tdK+vBkDas5 u4pRqvPtK619yrrKfHNYAPBOddzYm/XqjOCWEjmKcIw/YcsNrgtftJEl3A3Oi2uBHlct 5CuoeK/L0Cllvp3/1VRIoE8zAUKrSBpPnBfrcSMd+oMFDLlxx4rRX3k8CStKnzUDvgg3 ie8x7Q5M7PPH+2xHukY2sM0rSNrnhtRnbfH/ZxmsCnuQx3BIO4btY8/oYwhwTKq9U8dB XJsA== 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=YiJEB0dRG8Vs28wunrpsUd3aNm5kWfCeFbd3eFY3as0=; b=Ez38Ag39gMJL0mqqE2Cxda6jomPtwrpupw4X52bxN9iwPsEpL7w6BcuGasIpNGcCJ8 QO3jNbuqMkn3DTVxbPe3kx5OMv7b1ci11vs/NuMSu178bwpPhBWB9S38r+eKUrEfEYm5 16CxrwscYsQH9oPsU5GW/qYAlWlIJSJ7uvq92nZN1x5dePhcB5+g+EqFp2c8m1vlvpAZ UHTIj8wCv7ZIMaJnLJE9TjvTwq01LvI/xZrOYHEIkLQ7QDFmiGbJysjt/fXIwO6+u5JH AzezYh8GYdq2dfCy3QHt+I79zRmRvIcdX1BdKXkj7m+zLeW+7rxVqLK4HVbEbhZu6n1O 1hcw== X-Gm-Message-State: AOAM5328HsyZpbrHf/r06e18vSN7b+It2yCJj+6p3Zbc+Kb06NvBSU8R FA2y+tyU3yG5fH2LoPHNzGqLVhbHck2mlUQcWkAS3g== X-Google-Smtp-Source: ABdhPJzkXr9BOqsgJAkCTK7/ifPaSnlqKx7Ilm0RuLZ18kZbUoUwyM07wgDkFY+vVJrPQc3/yTK2PG51XyTTjydMhQs= X-Received: by 2002:ab0:482d:0:b0:35d:1e5e:ed19 with SMTP id b42-20020ab0482d000000b0035d1e5eed19mr6553573uad.17.1650956413953; Tue, 26 Apr 2022 00:00:13 -0700 (PDT) MIME-Version: 1.0 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-13-yuzhao@google.com> <20220411191634.674554d3de2ba37b3db40ca2@linux-foundation.org> <20220415212024.c682ac000e3e91572d8d6d2b@linux-foundation.org> In-Reply-To: <20220415212024.c682ac000e3e91572d8d6d2b@linux-foundation.org> From: Yu Zhao Date: Tue, 26 Apr 2022 00:59:37 -0600 Message-ID: Subject: Re: [PATCH v10 12/14] mm: multi-gen LRU: debugfs interface To: Andrew Morton Cc: Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Linus Torvalds , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , Linux ARM , "open list:DOCUMENTATION" , linux-kernel , Kernel Page Reclaim v2 , "the arch/x86 maintainers" , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 67F1E40047 X-Stat-Signature: 3wxzf5rgg6wro89f5i356fc1ij71yzjn X-Rspam-User: Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=d5Yk9vkB; spf=pass (imf11.hostedemail.com: domain of yuzhao@google.com designates 209.85.222.48 as permitted sender) smtp.mailfrom=yuzhao@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1650956412-769601 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 Fri, Apr 15, 2022 at 10:20 PM Andrew Morton wrote: > > On Fri, 15 Apr 2022 18:03:16 -0600 Yu Zhao wrote: > > > > Presumably sysfs is the place. Fully documented and with usage > > > examples in the changelog so we can carefully review the proposed > > > extensions to Linux's ABI. Extensions which must be maintained > > > unchanged for all time. > > > > Eventually, yes. There still is a long way to go. Rest assured, this > > is something Google will keep investing resources on. > > So. The plan is to put these interfaces in debugfs for now, with a > view to migrating stabilized interfaces into sysfs (or procfs or > whatever) once end-user requirements and use cases are better > understood? The requirements are well understood and the use cases are proven, e.g., Google [1], Meta [2] and Alibaba [3]. [1] https://dl.acm.org/doi/10.1145/3297858.3304053 [2] https://dl.acm.org/doi/10.1145/3503222.3507731 [3] https://gitee.com/anolis/cloud-kernel/blob/release-5.10/mm/kidled.c > If so, that sounds totally great to me. But it should have been in > the darn changelog! This is the sort of thing which we care about most > keenly. > > It would be helpful for reviewers to understand the proposed timeline > for this process, because the entire feature isn't really real until > this is completed, is it? I do think we should get this nailed down > relatively rapidly, otherwise people will be reluctant to invest much > into a moving target. > > And I must say, I see dissonance between the overall maturity of the > feature as described in these emails versus the immaturity of these > userspace control interfaces. What's happening there? Very observant. To answer both of the questions above: each iteration of the entire stack is a multi-year effort. Given its ROI, companies I know of constantly pour money into this area. Given its scale, this debugfs is the least of their concerns. A good example is the proactive reclaim sysfs interface [4]. It's been used at Google for many years and at Meta for a few years. We only started finalizing it recently. [4] https://lore.kernel.org/r/20220425190040.2475377-1-yosryahmed@google.com/