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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed, 2 Nov 2022 13:07:22 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Sergey Senozhatsky <senozhatsky@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Nitin Gupta <ngupta@vflare.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCHv4 0/9] zram: Support multiple compression streams
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References: <20221018045533.2396670-1-senozhatsky@chromium.org>
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On Tue, Oct 18, 2022 at 01:55:24PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> 	This series adds support for multiple (per-CPU)
> compression streams (at point only 2). The main idea is that
> different compression algorithms have different characteristics
> and zram may benefit when it uses a combination of algorithms:
> a default algorithm that is faster but have lower compression
> rate and a secondary algorithm that can use higher compression
> rate at a price of slower compression/decompression.
> 
> 	There are several use-case for this functionality:
> 
> - huge pages re-compression: zstd or deflate can successfully
> compress huge pages (~50% of huge pages on my synthetic ChromeOS
> tests), IOW pages that lzo was not able to compress.
> 
> - idle pages re-compression: idle/cold pages sit in the memory
> and we may reduce zsmalloc memory usage if we recompress those
> idle pages.
> 
> 	User-space has a number of ways to control the behavior
> and impact of zram recompression: what type of pages should be
> recompressed, size watermarks, etc. Please refer to documentation
> patch.

Hi Sergey,

First of all, I am really sorry to attend the party too late.

I absolutely agree the feature is really useful and even I am
thinking to support multiple comression trials on the fly for
future. So I'd like to introduce the feature more general shape
to be extended later so review will go.

Thanks!