Re: [PATCH v2] xentop: add support for qdisks

[Ian Campbell <ian.campbell@citrix.com>]

On Thu, 2015-03-19 at 13:20 -0600, Charles Arnold wrote:
> >>> On 3/19/2015 at 12:09 PM, Anthony PERARD <anthony.perard@citrix.com> wrote: 
> > On Wed, Mar 18, 2015 at 04:12:26PM +0000, Ian Campbell wrote:
> >> My second concern here is with the use of /var/run/xen/qmp-libxl-%i from
> >> outside of libxl. I can't remember if qemu is safe against multiple
> >> users of the socket. ISTR asking Anthony this before, but I don't recall
> >> the answer, sorry :-(
> > 
> > Last time I checked, only one client at a time can connect to the socket.
> > If a second user want to connect to the socket, it will be blocked until
> > the first one disconnect.
> 
> This seems correct based on some of my testing.  In rare cases (perhaps not so
> rare for VMs under heavy I/O load), reading the socket to get the stats times out
> and so xentop will report '0' for the read/write stats until the next read attempt
> that succeeds.
> 
> It looks as if we do need a second socket to qemu.  I will include that in the next
> patch version.

Yep, it sounds like it is a requirement, thanks.

Ian.