linux-kernel - Re: [PATCHv4 0/9] zsmalloc/zram: configurable zspage size

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Message-ID: <Y3H+WGCH4Xgh21PD@google.com>
Date:   Mon, 14 Nov 2022 17:37:44 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCHv4 0/9] zsmalloc/zram: configurable zspage size

On (22/11/11 09:03), Minchan Kim wrote:
[..]
> for class in classes:
>     wasted_bytes += class->pages_per_zspage * PAGE_SIZE - an object size
> 
> with *aggressive zpage compaction*. Now, we are relying on shrinker
> (it might be already enough) to trigger but we could change the policy 
> wasted memory in the class size crossed a threshold

That threshold can be another tunable in zramX/allocator_tunables sysfs
knob and struct zs_tunables.

But overall it sounds like a bigger project for some time next year.
We already have zs_compact() sysfs knob, so user-space can invoke it
as often as it wants to (not aware if anyone does btw), maybe new
compaction should be something slightly different. I don't have any
ideas yet. One way or the other it still can use the same sysfs knob :)