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Date:   Mon, 22 May 2023 15:04:46 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Kent Overstreet <kent.overstreet@linux.dev>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-bcachefs@vger.kernel.org, Dave Chinner <dchinner@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 22/32] vfs: inode cache conversion to hash-bl
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On Wed, May 17, 2023 at 09:15:34AM +1000, Dave Chinner wrote:
> On Tue, May 16, 2023 at 12:17:04PM -0400, Kent Overstreet wrote:
> > On Tue, May 16, 2023 at 05:45:19PM +0200, Christian Brauner wrote:
> > > On Wed, May 10, 2023 at 02:45:57PM +1000, Dave Chinner wrote:
> > > There's a bit of a backlog before I get around to looking at this but
> > > it'd be great if we'd have a few reviewers for this change.
> > 
> > It is well tested - it's been in the bcachefs tree for ages with zero
> > issues. I'm pulling it out of the bcachefs-prerequisites series though
> > since Dave's still got it in his tree, he's got a newer version with
> > better commit messages.
> > 
> > It's a significant performance boost on metadata heavy workloads for any
> > non-XFS filesystem, we should definitely get it in.
> 
> I've got an up to date vfs-scale tree here (6.4-rc1) but I have not
> been able to test it effectively right now because my local
> performance test server is broken. I'll do what I can on the old
> small machine that I have to validate it when I get time, but that
> might be a few weeks away....
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs.git vfs-scale
> 
> As it is, the inode hash-bl changes have zero impact on XFS because
> it has it's own highly scalable lockless, sharded inode cache. So
> unless I'm explicitly testing ext4 or btrfs scalability (rare) it's
> not getting a lot of scalability exercise. It is being used by the
> root filesytsems on all those test VMs, but that's about it...

I think there's a bunch of perf tests being run on -next. So we can
stuff it into a vfs.unstable.* branch and see what -next thinks of this
performance wise.