linux-kernel - Re: [PATCH] mm: limit THP alignment – performance gain observed in AI inference workloads

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Message-ID: <04a109b1-8f60-45e3-b8d3-70bd849ee877@lucifer.local>
Date: Tue, 1 Jul 2025 14:28:40 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: siddhartha@...ip.in
Cc: Dev Jain <dev.jain@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, mgorman@...e.de
Subject: Re: [PATCH] mm: limit THP alignment – performance gain observed in AI inference workloads

On Tue, Jul 01, 2025 at 06:53:47PM +0530, siddhartha@...ip.in wrote:
> Hi Lorenzo,
>
> Thanks for your clarification, and I appreciate your patience — especially
> given your role in maintaining and designing the VMA merge logic.
>
> I understand now that my earlier phrasing may have repeated your explanation
> for VMA adjacency, and I regret unintentionally restating it.
>
> I’ll make sure to be more careful and direct going forward.

Thanks, no problem. Mostly avoids confusion.

>
> As for the THP alignment condition now being `IS_ALIGNED(len, PMD_SIZE)`, I
> agree this resolves the regressions by removing alignment for non-aligned
> sizes, which was exactly what broke workloads like cactusBSSN or some AI
> inference loads.

Ack - we're really happy to hear about workloads that this has helped as this
kind of input is very important as to getting insight into how THP-related stuff
impacts real users so we can best optimise especially for workloads that are
very important in the industry right now.

>
> Thanks again for the guidance — I’m learning a lot from this thread.

Glad to have helped, thanks again for reporting!

>
> Best Regards,
> Siddhartha Sharma
>

Cheers, Lorenzo