linux-kernel - Re: [PATCH v7 0/6] Implement writeback for zsmalloc

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Date:   Tue, 3 Jan 2023 04:57:30 +0000
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Nhat Pham <nphamcs@...il.com>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, minchan@...nel.org,
        ngupta@...are.org, senozhatsky@...omium.org, sjenning@...hat.com,
        ddstreet@...e.org, vitaly.wool@...sulko.com, linux@...ssschuh.net
Subject: Re: [PATCH v7 0/6] Implement writeback for zsmalloc

Hi,

On Mon, Nov 28, 2022 at 11:16:09AM -0800, Nhat Pham wrote:
> Unlike other zswap's allocators such as zbud or z3fold, zsmalloc
> currently lacks the writeback mechanism. This means that when the zswap
> pool is full, it will simply reject further allocations, and the pages
> will be written directly to swap.
> 
> This series of patches implements writeback for zsmalloc. When the zswap
> pool becomes full, zsmalloc will attempt to evict all the compressed
> objects in the least-recently used zspages.

Then this part of Documentation/admin-guide/mm/zswap.rst should probably
also be updated at some point:

    However, zsmalloc does not implement compressed page eviction, so
    once zswap fills it cannot evict the oldest page, it can only reject
    new pages.

Thomas