linux-kernel - Re: [RFC 2/3] mm: introduce GCMA

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Message-ID: <CAJuCfpF=fk3=s3NLkai0GN5twjgY8AyyL1vZn3T+N7E10SgHug@mail.gmail.com>
Date: Fri, 21 Mar 2025 09:13:09 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: akpm@...ux-foundation.org, willy@...radead.org, david@...hat.com, 
	vbabka@...e.cz, lorenzo.stoakes@...cle.com, liam.howlett@...cle.com, 
	alexandru.elisei@....com, peterx@...hat.com, hannes@...xchg.org, 
	mhocko@...nel.org, m.szyprowski@...sung.com, iamjoonsoo.kim@....com, 
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	sourabhjain@...ux.ibm.com, ritesh.list@...il.com, aneesh.kumar@...nel.org, 
	bhelgaas@...gle.com, sj@...nel.org, fvdl@...gle.com, ziy@...dia.com, 
	yuzhao@...gle.com, minchan@...nel.org, linux-mm@...ck.org, 
	linuxppc-dev@...ts.ozlabs.org, linux-block@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, iommu@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Minchan Kim <minchan@...gle.com>
Subject: Re: [RFC 2/3] mm: introduce GCMA

On Thu, Mar 20, 2025 at 10:14 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Thu, Mar 20, 2025 at 10:39:30AM -0700, Suren Baghdasaryan wrote:
> > From: Minchan Kim <minchan@...gle.com>
> >
> > This patch introduces GCMA (Guaranteed Contiguous Memory Allocator)
> > cleacache backend which reserves some amount of memory at the boot
> > and then donates it to store clean file-backed pages in the cleancache.
> > GCMA aims to guarantee contiguous memory allocation success as well as
> > low and deterministic allocation latency.
> >
> > Notes:
> > Originally, the idea was posted by SeongJae Park and Minchan Kim [1].
> > Later Minchan reworked it to be used in Android as a reference for
> > Android vendors to use [2].
>
> That is not a very good summay.  It needs to explain how you ensure
> that the pages do stay clean forever.

Sure, I'm happy to improve the description. Do you want more details
about how only clean pages end up in the cleancache and how they get
invalidated once the original page gets modified? Or is the concern
that donated pages might be changed by the donor without taking them
away from the cleancache?

>