linux-kernel - Re: [PATCH v10 12/14] mm: multi-gen LRU: debugfs interface

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Message-ID: <CAOUHufYhhCPFqoRbtn+=OFxZxNWS9yxW9Re_s-2TYGqCEaMXVw@mail.gmail.com>
Date:   Fri, 15 Apr 2022 18:03:16 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Stephen Rothwell <sfr@...hwell.id.au>,
        Linux-MM <linux-mm@...ck.org>, Andi Kleen <ak@...ux.intel.com>,
        Aneesh Kumar <aneesh.kumar@...ux.ibm.com>,
        Barry Song <21cnbao@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Michael Larabel <Michael@...haellarabel.com>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Will Deacon <will@...nel.org>,
        Ying Huang <ying.huang@...el.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Kernel Page Reclaim v2 <page-reclaim@...gle.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Brian Geffon <bgeffon@...gle.com>,
        Jan Alexander Steffens <heftig@...hlinux.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Steven Barrett <steven@...uorix.net>,
        Suleiman Souhlal <suleiman@...gle.com>,
        Daniel Byrne <djbyrne@....edu>,
        Donald Carr <d@...os-reins.com>,
        Holger Hoffstätte <holger@...lied-asynchrony.com>,
        Konstantin Kharlamov <Hi-Angel@...dex.ru>,
        Shuang Zhai <szhai2@...rochester.edu>,
        Sofia Trinh <sofia.trinh@....works>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>
Subject: Re: [PATCH v10 12/14] mm: multi-gen LRU: debugfs interface

On Mon, Apr 11, 2022 at 8:16 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed,  6 Apr 2022 21:15:24 -0600 Yu Zhao <yuzhao@...gle.com> wrote:
>
> > Add /sys/kernel/debug/lru_gen for working set estimation and proactive
> > reclaim. These features are required to optimize job scheduling (bin
> > packing) in data centers [1][2].
>
> debugfs is for ephemeral temp stuf which can and will change or
> disappear at any time.  Anything which is "required" by userspace
> should not be in debufgs.

Right. "required" is probably a poor choice of words. "These
techniques are commonly used to optimize job scheduling" would sound
better.

> 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.