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Date:   Wed, 16 Feb 2022 14:50:09 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Patrick Goetz <pgoetz@math.utexas.edu>
Cc:     "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: How are client requests load balanced across multiple nfsd
 processes?
Message-ID: <20220216195009.GC29074@fieldses.org>
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On Wed, Feb 16, 2022 at 01:33:55PM -0600, Patrick Goetz wrote:
> On 2/16/22 13:22, J. Bruce Fields wrote:
> >There's no user process that calls "listen"; knfsd's normal rpc handling
> >is all in-kernel.  Incoming rpc's may be handed to any of those 16 tasks
> >for processing.  A single task just runs a loop where it receives an
> >rpc, handles it, and sends a response back.
> >
> 
> How does knfsd decide what user space nfsd process to hand a task
> off to?

To be clear, knfsd tasks never run in userspace at all.

> Is it random, round robin, or something more sophisticated?

It's complicated, and I'd have to look at the code.  It's an
implementation detail that nobody should have to depend on.

> Or does it even matter if nfsd is only handling one request at a
> time anyway?

If you're running with 16 threads, then it can be (oversimplifying a
bit) handling up to 16 requests at a time.

--b.