linux-kernel - Re: [RFC PATCH 0/2] SKSM: Synchronous Kernel Samepage Merging

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Message-ID: <029759d4-f7b2-4ec6-b5d0-7c8a1c0fbd80@redhat.com>
Date: Fri, 28 Feb 2025 14:59:37 +0100
From: David Hildenbrand <david@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 Matthew Wilcox <willy@...radead.org>, Olivier Dion <odion@...icios.com>,
 linux-mm@...ck.org
Subject: Re: [RFC PATCH 0/2] SKSM: Synchronous Kernel Samepage Merging

On 28.02.25 06:17, Linus Torvalds wrote:
> On Thu, 27 Feb 2025 at 19:03, Mathieu Desnoyers
> <mathieu.desnoyers@...icios.com> wrote:
>>
>> I'd be fine with SKSM replacing KSM entirely. However, I don't
>> think we should try to re-implement the existing KSM userspace ABIs
>> over SKSM.
> 
> No, absolutely. The only point (for me) for your new synchronous one
> would be if it replaced the kernel thread async scanning, which would
> make the old user space interface basically pointless.
> 
> But I don't actually know who uses KSM right now. My reaction really
> comes from a "it's not nice code in the kernel", not from any actual
> knowledge of the users.
> 
> Maybe it works really well in some cloud VM environment, and we're
> stuck with it forever.

Exactly that; and besides the VM use-case, lately people stated using it 
in the context of interpreters (IIRC inside Meta) quite successfully as 
well.

-- 
Cheers,

David / dhildenb