From: Rick Macklem <rick.macklem@gmail.com>
To: Chuck Lever <cel@kernel.org>
Cc: Cedric Blancher <cedric.blancher@gmail.com>,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: Increase default NFSv4 server size "max_block_size" to 4MB
Date: Mon, 16 Mar 2026 16:35:34 -0700 [thread overview]
Message-ID: <CAM5tNy7GG0awNYYJWv0968e5CMoUstr0GcrNwuNKP4x3Yrp3JQ@mail.gmail.com> (raw)
In-Reply-To: <5acaa8e7-0691-4cbd-b501-c26831a7be81@app.fastmail.com>
On Mon, Mar 16, 2026 at 5:41 AM Chuck Lever <cel@kernel.org> wrote:
>
>
> On Mon, Mar 16, 2026, at 3:51 AM, Cedric Blancher wrote:
> > As debated a while ago, can the default NFSv4 server size for
> > "max_block_size" be increased to 4MB, please?
>
> There is an administrative setting to raise this limit for
> recent versions of the kernel. Can you report your experience
> when you raise the limit? Hiccups, performance issues, etc? I
> would kind of like this exercise to be data-driven.
>
> What is still unknown to me is which NFS client implementations
> can support 4MB or 8MB. Without client support, an increase in
> the default in NFSD doesn't mean anything. Rick, Anna, Roland?
Although it has not seen much testing, it is possible to do a > 1Mbyte NFSv4
mount in FreeBSD.
For a 2Mbyte mount, (the only size > 1Mbyte I've tried) the settings would be..
In /boot/loader.conf
kern.maxphys=2097152
vfs.maxbcachebuf=2097152
and in /etc/sysctl.conf
kern.ipc.maxsockbuf=9455616
Then a mount will use 2Mbytes if the server supports it.
I doubt anyone does this, but it works for trivial tests.
Maybe I'll do it during the next bakeathon? rick
ps:It would be really nice if Roland could show up
(you can attend remotely via tailscale like I do)
at the next bakeathon.
>
> --
> Chuck Lever
>
next prev parent reply other threads:[~2026-03-16 23:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-16 7:51 Increase default NFSv4 server size "max_block_size" to 4MB Cedric Blancher
2026-03-16 12:39 ` Chuck Lever
2026-03-16 14:40 ` Roland Mainz
2026-03-16 23:35 ` Rick Macklem [this message]
2026-05-12 13:18 ` Increase FreeBSD NFSv4 nfsd buffer size? " Cedric Blancher
2026-05-12 23:02 ` Rick Macklem
2026-05-13 8:37 ` Cedric Blancher
2026-05-13 23:38 ` Rick Macklem
2026-05-14 22:39 ` Rick Macklem
2026-05-14 22:52 ` vermaden
2026-05-14 23:49 ` Rick Macklem
2026-03-17 13:51 ` Anna Schumaker
2026-03-30 18:46 ` Mike Snitzer
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