[Virtio-fs] [PATCH 2/2] fuse: virtiofs: Add basic multiqueue support
Chirantan Ekbote
chirantan at chromium.org
Thu May 7 08:10:15 UTC 2020
On Sat, May 2, 2020 at 12:48 AM Stefan Hajnoczi <stefanha at redhat.com> wrote:
>
> On Fri, May 01, 2020 at 04:14:38PM +0900, Chirantan Ekbote wrote:
> > On Tue, Apr 28, 2020 at 12:20 AM Stefan Hajnoczi <stefanha at redhat.com> wrote:
> > > Instead of modifying the guest driver, please implement request
> > > parallelism in your device implementation.
> >
> > Yes, we have tried this already [1][2]. As I mentioned above, having
> > additional threads in the server actually made performance worse. My
> > theory is that when the device only has 2 cpus, having additional
> > threads on the host that need cpu time ends up taking time away from
> > the guest vcpu. We're now looking at switching to io_uring so that we
> > can submit multiple requests from a single thread.
>
> The host has 2 CPUs? How many vCPUs does the guest have? What is the
> physical storage device? What is the host file system?
The host has 2 cpus. The guest has 1 vcpu. The physical storage
device is an internal ssd. The file system is ext4 with directory
encryption.
>
> io_uring's vocabulary is expanding. It can now do openat2(2), close(2),
> statx(2), but not mkdir(2), unlink(2), rename(2), etc.
>
> I guess there are two options:
> 1. Fall back to threads for FUSE operations that cannot yet be done via
> io_uring.
> 2. Process FUSE operations that cannot be done via io_uring
> synchronously.
>
I'm hoping that using io_uring for just the reads and writes should
give us a big enough improvement that we can do the rest of the
operations synchronously.
Chirantan
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