linux-kernel - Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory

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Message-ID: <a7781f13-21ca-48c7-99c4-22beef0400f9@arm.com>
Date:   Fri, 20 Oct 2023 13:33:38 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory

On 06/10/2023 21:06, David Hildenbrand wrote:
> On 29.09.23 13:44, Ryan Roberts wrote:
>> Hi All,
> 

[...]

>> NOTE: These changes should not be merged until the prerequisites are complete.
>> These are in progress and tracked at [7].
> 
> We should probably list them here, and classify which one we see as strict a
> requirement, which ones might be an optimization.
> 

Bringing back the discussion of prerequistes to this thread following the
discussion at the mm-alignment meeting on Wednesday.

Slides, updated following discussion to reflect all the agreed items that are
prerequisites and enhancements, are at [1].

I've taken a closer look at the situation with khugepaged, and can confirm that
it does correctly collapse anon small-sized THP into PMD-sized THP. I did notice
though, that one of the khugepaged selftests (collapse_max_ptes_none) fails when
small-sized THP is enabled+always. So I've fixed that test up and will add the
patch to the next version of my series.

So I believe the khugepaged prerequisite can be marked as done.

[1]
https://drive.google.com/file/d/1GnfYFpr7_c1kA41liRUW5YtCb8Cj18Ud/view?usp=sharing&resourcekey=0-U1Mj3-RhLD1JV6EThpyPyA

Thanks,
Ryan