linux-kernel - Re: [PATCH 0/2] mm, swap: improve cluster scan strategy

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Message-ID: <CAF8kJuO-kVXb39AU-gFVYG8VOjfdVind5J28KUpeXHHPA4UYXg@mail.gmail.com>
Date: Tue, 5 Aug 2025 16:26:09 -0700
From: Chris Li <chrisl@...nel.org>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Kemeng Shi <shikemeng@...weicloud.com>, Nhat Pham <nphamcs@...il.com>, 
	Baoquan He <bhe@...hat.com>, Barry Song <baohua@...nel.org>, 
	"Huang, Ying" <ying.huang@...ux.alibaba.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] mm, swap: improve cluster scan strategy

On Mon, Aug 4, 2025 at 10:24 AM Kairui Song <ryncsn@...il.com> wrote:
>
> From: Kairui Song <kasong@...cent.com>
>
> This series improves the large allocation performance and reduces
> the failure rate. Some design of the cluster alloactor was later
> found to be improvable after thorough testing.

Nit: If you have a next version of this series, please include a bit
of detail on how you get the improvement to kick off the discussion.
Right now the cover letter just said I have some cool changes and here
is the number. e.g. limit the fragment list search to the first
cluster.

>
> For example, build kernel test with make -j96 and 10G ZRAM with 64kB
> mTHP enabled shows better performance and a lower failure rate:
>
> Before: sys time: 10230.22s  64kB/swpout: 1793044  64kB/swpout_fallback: 17653
> After:  sys time: 5538.3s    64kB/swpout: 1813133  64kB/swpout_fallback: 0
>
> System time is cut in half, and the failure rate drops to zero. Larger
> allocations in a hybrid workload also showed a major improvement:

That is a big improvement. Congrats.

>
> 512kB swap failure rate:
> Before: swpout:11971  swpout_fallback:2218
> After:  swpout:14606  swpout_fallback:4
>
> 2M swap failure rate:
> Before: swpout:12     swpout_fallback:1578
> After:  swpout:1253   swpout_fallback:15

The number looks very good.

Chris



Chris