linux-kernel - Re: [PATCH v6] zswap: memcontrol: implement zswap writeback disabling

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Date:   Fri, 8 Dec 2023 11:57:29 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Nhat Pham <nphamcs@...il.com>
Cc:     tj@...nel.org, lizefan.x@...edance.com, hannes@...xchg.org,
        cerasuolodomenico@...il.com, yosryahmed@...gle.com,
        sjenning@...hat.com, ddstreet@...e.org, vitaly.wool@...sulko.com,
        mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com,
        muchun.song@...ux.dev, hughd@...gle.com, corbet@....net,
        konrad.wilk@...cle.com, senozhatsky@...omium.org, rppt@...nel.org,
        linux-mm@...ck.org, kernel-team@...a.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        david@...t.cz, chrisl@...nel.org
Subject: Re: [PATCH v6] zswap: memcontrol: implement zswap writeback
 disabling

On Thu, 7 Dec 2023 16:42:59 -0800 Nhat Pham <nphamcs@...il.com> wrote:

> >
> > Also, it would be quite helpful of the changelog were to give us some
> > idea of how important this tunable is.  What sort of throughput
> > differences might it cause and under what circumstances?
> 
> For the most part, this feature is motivated by internal parties who
> have already established their opinions regarding swapping - the
> workloads that are highly sensitive to IO, and especially those who
> are using servers with really slow disk performance (for instance,
> massive but slow HDDs). For these folks, it's impossible to convince
> them to even entertain zswap if swapping also comes as a packaged
> deal. Writeback disabling is quite a useful feature in these
> situations - on a mixed workloads deployment, they can disable
> writeback for the more IO-sensitive workloads, and enable writeback
> for other background workloads.
> 
> (Maybe we should include the paragraph above as part of the changelog?)

I pasted it in, thanks.