linux-kernel - Re: ext4 writeback performance issue in 6.12

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Message-ID: <20251009172153.kx72mao26tc7v2yu@matt-Precision-5490>
Date: Thu, 9 Oct 2025 18:21:53 +0100
From: Matt Fleming <matt@...dmodwrite.com>
To: Jan Kara <jack@...e.cz>
Cc: adilger.kernel@...ger.ca, kernel-team@...udflare.com,
	libaokun1@...wei.com, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	tytso@....edu, willy@...radead.org
Subject: Re: ext4 writeback performance issue in 6.12

On Thu, Oct 09, 2025 at 02:29:07PM +0200, Jan Kara wrote:
> 
> OK, so even if we reduce the somewhat pointless CPU load in the allocator
> you aren't going to see substantial increase in your writeback throughput.
> Reducing the CPU load is obviously a worthy goal but I'm not sure if that's
> your motivation or something else that I'm missing :).
 
I'm not following. If you reduce the time it takes to allocate blocks
during writeback, why will that not improve writeback throughput?

Thanks,
Matt