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

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Message-ID: <20251014101346.ep73uuigr25xu5a2@matt-Precision-5490>
Date: Tue, 14 Oct 2025 11:13:46 +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 Fri, Oct 10, 2025 at 07:23:54PM +0200, Jan Kara wrote:
> 
> Maybe I misunderstood what you wrote about your profiles but you wrote that
> we were spending about 4% of CPU time in the block allocation code. Even if
> we get that close to 0%, you'd still gain only 4%. Or am I misunderstanding
> something?

Ah, I see. Yeah that's true but that's 4% of CPU cycles that could be
put to better use elsehwere :D