Re: [PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool

[Stefan Hajnoczi]

On Mon, Nov 09, 2020 at 09:35:48AM -0500, Vivek Goyal wrote:
> Right now we create a thread pool and main thread hands over the request
> to thread in thread pool to process. Number of threads in thread pool
> can be managed by option --thread-pool-size.
> 
> In tests we have noted that many of the workloads are getting better
> performance if we don't use a thread pool at all and process all
> the requests in the context of a thread receiving the request.
> 
> Hence give user an option to be able to run virtiofsd without using
> a thread pool.
> 
> To implement this, I have used existing option --thread-pool-size. This
> option defines how many maximum threads can be in the thread pool.
> Thread pool size zero freezes thead pool. I can't see why will one
> start virtiofsd with a frozen thread pool (hence frozen file system).
> So I am redefining --thread-pool-size=0 to mean, don't use a thread pool.
> Instead process the request in the context of thread receiving request
> from the queue.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)

This is useful for benchmarking. For production we need to understand
the cause of the performance difference so that virtiofsd can adapt to
the workload without setting a specific thread-pool-size value.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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