linux-kernel - Re: [PATCH 0/2] fix MADV_COLLAPSE issue if THP settings are disabled

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Message-ID: <60a81a60-b7da-4439-b177-9d1bca82828d@lucifer.local>
Date: Fri, 30 May 2025 10:34:36 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>, akpm@...ux-foundation.org,
        hughd@...gle.com, Liam.Howlett@...cle.com, npache@...hat.com,
        dev.jain@....com, ziy@...dia.com, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] fix MADV_COLLAPSE issue if THP settings are disabled

On Fri, May 30, 2025 at 11:16:51AM +0200, David Hildenbrand wrote:
[snip]
> It kind-of contradicts the linked
> Documentation/admin-guide/mm/transhuge.rst, where we have this *beautiful*
> comment
>
> "Transparent Hugepage Support for anonymous memory can be entirely disable
> (mostly for debugging purposes".
>
> I mean, "entirely" is also pretty clear to me.
>
> I would assume that the man page of MADV_COLLAPSE should have talked about
> ignoring *khugepaged* toggles (max_ptes_none ...), at least that's what I
> recall from the discussions back then.

Sorry I don't want to turn this stuff into too much of a mega-thread but
just a small comment here - I think we should go and update the
documentation/man pages to be clearer and consistent.

There is enough confusion around this as it is...

>
> --
> Cheers,
>
> David / dhildenb
>