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

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Message-ID: <Y3w8/q/HoSbqamoD@google.com>
Date:   Tue, 22 Nov 2022 12:07:42 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Alexey Romanov <avromanov@...rdevices.ru>, minchan@...nel.org,
        ngupta@...are.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel@...rdevices.ru,
        ddrokosov@...rdevices.ru,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [RFC PATCH v1 0/4] Introduce merge identical pages mechanism

On (22/11/22 12:00), Sergey Senozhatsky wrote:
> On (22/11/21 15:44), Johannes Weiner wrote:
> > This looks pretty great.
> > 
> > However, I'm curious why it's specific to zram, and not part of
> > zsmalloc? That way zswap would benefit as well, without having to
> > duplicate the implementation. This happened for example with
> > page_same_filled() and zswap_is_page_same_filled().
> > 
> > It's zsmalloc's job to store content efficiently, so couldn't this
> > feature (just like the page_same_filled one) be an optimization that
> > zsmalloc does transparently for all its users?
> 
> Yea, that's a much needed functionality, but things may be "complicated".
> We had that KSM-ish thing in the past in zram. Very briefly as we quickly
> found out that the idea was patented by some company in China and we couldn't
> figure our if it was safe to land that code upstream. So we ended up dropping
> the patches.
> 
> https://lore.kernel.org/lkml/1494556204-25796-1-git-send-email-iamjoonsoo.kim@lge.com/

IIRC that was patent in question:

https://patentimages.storage.googleapis.com/e2/66/9e/0ddbfae5c182ac/US9977598.pdf