[PATCH] qemu: virtiofs: Add pool element to limit thread pool

[Peter Krempa]

On Tue, Oct 20, 2020 at 13:54:33 -0400, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma at jp.fujitsu.com>
> 
> virtiofsd has --thread-pool-size=NUM option to limit the
> thread pool size. It will be useful to tune the performance.

Usually it's great to document or at least link to a document which
outlines how changing the parameter influences performance. In many
cases theres just one good option and that should become default. In
other cases it depends on deployment and in such case it's very good to
prevent users from having to guess what it actually does.

In the end it serves as a justification that adding a tuning knob is
worth it.

> Add pool element to use the option like as:
> 
>    <filesystem type='mount' accessmode='passthrough'>
>        <driver type='virtiofs' queue='1024'/>
>        <binary path='/usr/libexec/virtiofsd' xattr='on' pool='32'/>

I'd prefer if the attribute is named 'threads' as that seems to me to be
more clear what it does without having to refer back to the
documentation.


>        <source dir='/path'/>
>        <target dir='mount_tag'/>
>    </filesystem>
> 
> Signed-off-by: Masayoshi Mizuma <m.mizuma at jp.fujitsu.com>
> ---