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

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Message-ID: <CAKEwX=MPxEsCJ8V8vNvMgXJ66Pq7qxnOX6S1sf97dc-oqaJfWQ@mail.gmail.com>
Date:   Fri, 6 Jan 2023 12:32:04 -0800
From:   Nhat Pham <nphamcs@...il.com>
To:     Thomas Weißschuh <thomas@...ch.de>
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

On Mon, Jan 2, 2023 at 8:57 PM Thomas Weißschuh <thomas@...ch.de> wrote:
>
> 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

Thanks for pointing this out, Thomas! I'll send a patch to update this.