linux-kernel - Re: [RFC PATCH v1 0/4] Introduce merge identical pages mechanism

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Date:   Wed, 23 Nov 2022 13:13:55 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Aleksey Romanov <AVRomanov@...rdevices.ru>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Johannes Weiner <hannes@...xchg.org>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "ngupta@...are.org" <ngupta@...are.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        Dmitry Rokosov <DDRokosov@...rdevices.ru>
Subject: Re: [RFC PATCH v1 0/4] Introduce merge identical pages mechanism

On (22/11/22 12:14), Aleksey Romanov wrote:
> > IIRC that was patent in question:
> > 
> > https://patentimages.storage.googleapis.com/e2/66/9e/0ddbfae5c182ac/US9977598.pdf
> 
> I think the patent is talking about "mapping the virtual address" (like
> in KSM). But zram works with the "handle" abstraction, which is a boxed
> pointer to the required object. I think my implementation and the patent
> is slightly different. 
> 
> Also, the patent speaks of "compressing" pages. In this case, we can add
> zs_merge() function (like zs_compact()), that is, remove the merge logic
> at the allocator level. zsmalloc doesn't say anything about what objects
> it can work with. Implementation at the zsmalloc level is possible,
> though more complicated that at the zram level. 
> 
> I believe that we can implement at least one of the options I proposed.
> 
> What do you think?

Oh, yeah, I'm not saying that we cannot have something like that
in zram/zsmalloc, just wanted to give some historical retrospective
on this and point at some implementation details that should be
considered.