linux-ext4 - Re: [PATCHBOMB v6] fuse: containerize ext4 for safer operation

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Message-ID: <CAJnrk1YVjB2U6HSHqkjqCc_6i-Vzg+Vmts_KV0yaa3KG6TN3pg@mail.gmail.com>
Date: Thu, 30 Oct 2025 09:35:25 -0700
From: Joanne Koong <joannelkoong@...il.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: linux-fsdevel <linux-fsdevel@...r.kernel.org>, Miklos Szeredi <miklos@...redi.hu>, 
	Bernd Schubert <bernd@...ernd.com>, linux-ext4 <linux-ext4@...r.kernel.org>, 
	"Theodore Ts'o" <tytso@....edu>, Neal Gompa <neal@...pa.dev>, Amir Goldstein <amir73il@...il.com>, 
	Christian Brauner <brauner@...nel.org>, Jeff Layton <jlayton@...nel.org>
Subject: Re: [PATCHBOMB v6] fuse: containerize ext4 for safer operation

On Tue, Oct 28, 2025 at 5:27 PM Darrick J. Wong <djwong@...nel.org> wrote:
>
> At this stage I still get about 95% of the kernel ext4 driver's
> streaming directio performance on streaming IO, and 110% of its
> streaming buffered IO performance.  Random buffered IO is about 85% as

Do you know why this is faster than ext4 sequential buffered IO?

Thanks,
Joanne

> fast as the kernel.  Random direct IO is about 80% as fast as the
> kernel; see the cover letter for the fuse2fs iomap changes for more
> details.  Unwritten extent conversions on random direct writes are
> especially painful for fuse+iomap (~90% more overhead) due to upcall
> overhead.  And that's with (now dynamic) debugging turned on!
>