linux-kernel - Re: [PATCH v5 3/5] mm: LARGE_ANON

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Message-ID: <ZPCHpOtYgq32leay@casper.infradead.org>
Date:   Thu, 31 Aug 2023 13:29:24 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     "Huang, Ying" <ying.huang@...el.com>,
        Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.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>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 3/5] mm: LARGE_ANON_FOLIO for improved performance

On Thu, Aug 31, 2023 at 09:57:46AM +0200, David Hildenbrand wrote:
> As raised in another mail, we can then discuss
> * how we want to call this feature (transparent large pages? there is
>   the concern that "THP" might confuse users. Maybe we can consider
>   "large" the more generic version and "huge" only PMD-size, TBD)
> * how to expose it in stats towards the user (e.g., /proc/meminfo)
> * which minimal toggles we want
> 
> I think there *really* has to be a way to disable it for a running system,
> otherwise no distro will dare pulling it in, even after we figured out the
> other stuff.
> 
> Note that for the pagecache, large folios can be disabled and distributions
> are actively making use of that.

You can't.  Well, you can for shmem/tmpfs, but you have to edit the
source code or disable CONFIG_TRANSPARENT_HUGEPAGE to disable it for XFS.