linux-kernel - Re: [RFC 0/1] writeback: add sysfs to config the number of writeback contexts

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Message-ID: <77291508-cd85-4889-8502-73eb834e543c@samsung.com>
Date: Fri, 29 Aug 2025 14:29:57 +0530
From: Kundan Kumar <kundan.kumar@...sung.com>
To: wangyufei <wangyufei@...o.com>, Andrew Morton
	<akpm@...ux-foundation.org>, David Hildenbrand <david@...hat.com>, Lorenzo
	Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett"
	<Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport
	<rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko
	<mhocko@...e.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, Stephen
	Rothwell <sfr@...b.auug.org.au>, open list <linux-kernel@...r.kernel.org>,
	"open list:MEMORY MANAGEMENT - MISC" <linux-mm@...ck.org>, "open list:PAGE
 CACHE" <linux-fsdevel@...r.kernel.org>
Cc: anuj20.g@...sung.com, hch@....de, bernd@...ernd.com, djwong@...nel.org,
	jack@...e.cz, opensource.kernel@...o.com
Subject: Re: [RFC 0/1] writeback: add sysfs to config the number of
 writeback contexts

On 8/25/2025 5:59 PM, wangyufei wrote:
> Hi everyone,
> 
> We've been interested in this patch about parallelizing writeback [1]
> and have been following its discussion and development. Our testing in
> several application scenarios on mobile devices has shown significant
> performance improvements.
> 

Hi,

Thanks for sharing this work.

Could you clarify a few details about your test setup?

- Which filesystem did you run these experiments on?
- What were the specifics of the workload (number of threads, block size,
   I/O size)?
- If you are using fio, can you please share the fio command.
- How much RAM was available on the test system?
- Can you share the performance improvement numbers you observed?

That would help in understanding the impact of parallel writeback?

I made similar modifications to dynamically configure the number of
writeback threads in this experimental patch. Refer to patches 14 and 15:
https://lore.kernel.org/all/20250807045706.2848-1-kundan.kumar@samsung.com/
The key difference is that this change also enables a reduction in the
number of writeback threads.

Thanks,
Kundan

>