Re: [Virtio-fs] virtiofs vs 9p performance(Re: tools/virtiofs: Multi threading seems to hurt performance)

[Vivek Goyal]

On Tue, Sep 29, 2020 at 03:49:04PM +0200, Miklos Szeredi wrote:
> On Tue, Sep 29, 2020 at 3:18 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> 
> > - virtiofs cache=none mode is faster than cache=auto mode for this
> >   workload.
> 
> Not sure why.  One cause could be that readahead is not perfect at
> detecting the random pattern.  Could we compare total I/O on the
> server vs. total I/O by fio?

Ran tests with auto_inval_data disabled and compared with other results.

vtfs-auto-ex-randrw     randrw-psync            27.8mb/9547kb   7136/2386
vtfs-auto-sh-randrw     randrw-psync            43.3mb/14.4mb   10.8k/3709
vtfs-auto-sh-noinval    randrw-psync            50.5mb/16.9mb   12.6k/4330
vtfs-none-sh-randrw     randrw-psync            54.1mb/18.1mb   13.5k/4649

With auto_inval_data disabled, this time I saw around 20% performance jump
in READ and is now much closer to cache=none performance.

Thanks
Vivek