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Date: Tue, 2 Jun 2026 15:19:19 +0200
From: Christian Brauner <brauner@kernel.org>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: viro@zeniv.linux.org.uk, jack@suse.cz, linux-kernel@vger.kernel.org, 
	linux-fsdevel@vger.kernel.org, adobriyan@gmail.com
Subject: Re: [PATCH v4 0/3] revamp fs/filesystems.c
Message-ID: <20260602-eiskalt-kaputt-baubeginn-739632ab746b@brauner>
References: <20260529171840.2576445-1-mjguzik@gmail.com>
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In-Reply-To: <20260529171840.2576445-1-mjguzik@gmail.com>

On Fri, May 29, 2026 at 07:18:37PM +0200, Mateusz Guzik wrote:
> The file is a mess with a hand-rolled linked list in a desperate need of
> a clean up.
> 
> The code to emit /proc/filesystems is used frequently because libselinux
> reads the file, which in turn is linked into numerous frequently used
> programs (even ones you would not suspect, like sed!). In order to
> combat that pre-gen the string instead of pointer-chasing and printfing
> one by-one.
> 
> open+read+close cycle single-threaded (ops/s):
> before: 442732
> after:  1063462 (+140%)
> 
> Additionally scalability is also improved thanks to bypassing ref
> maintenance on open/close.
> 
> open+read+close cycle with 20 processes (ops/s):
> before: 606177
> after:	3300576 (+444%)
> 
> The main bottleneck afterwards is the spurious lockref trip on open.

There's a bunch of work in vfs-7.2.procfs on top of what's currently in
there. So please any changes should be a diff on there otherwise we have
to rebase that whole branch when it's already -rc6.