linux-kernel - Re: [RFC PATCH v3 7/8] mm/zswap: compressed ram direct integration

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Message-ID: <aWkkuaYt0cEyvbGj@gourry-fedora-PF4VCD3F>
Date: Thu, 15 Jan 2026 12:32:41 -0500
From: Gregory Price <gourry@...rry.net>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Nhat Pham <nphamcs@...il.com>, linux-mm@...ck.org,
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Subject: Re: [RFC PATCH v3 7/8] mm/zswap: compressed ram direct integration

On Thu, Jan 15, 2026 at 05:00:04PM +0000, Yosry Ahmed wrote:
> > 
> > 2. Just enable zswap shrinker and have memory reclaim move these pages
> > into disk swap. This will have a much more drastic performance
> > implications though :)
> 
> I think what you're getting it as that we can still make forward
> progress after memory lands in compressed cxl. But moving memory to
> compressed cxl is already forward progress that reclaim won't capture if
> we charge memory as a full page. I think this is the crux of the issue.
> 
> We need to figure out how to make accounting work such that moving
> memory to compressed cxl is forward progress, but make sure we don't
> break the overall accounting consisteny. If we only charge the actual
> compressed size, then from the system perspective there is a page that
> is only partially charged and the rest of it is more-or-less leaked.

Which is comically fine - because the actual capacity of the node is
functionally a lie anyway :D

~Gregory