Re: [libvirt] [REPOST 0/4] Adjustment to recent cgroup/cpuset changes (for 1.3.1)
On Wed, 13 Jan 2016 17:53:16 +0000
"Daniel P. Berrange" <berrange(a)redhat.com> wrote:
On Wed, Jan 13, 2016 at 05:51:34PM +0100, Martin Kletzander wrote:
> On Wed, Jan 13, 2016 at 07:29:46AM -0500, John Ferlan wrote:
> >Reposting my cgroup fixes series:
> >
> >http://www.redhat.com/archives/libvir-list/2016-January/msg00236.html
> >
> >partially because I originally forgot to CC the author (Henning
> >Schild) of the original series for which these patch fix a couple
> >of issues discovered during regression testing (virt-test memtune
> >failures in Red Hat regression environment), but also to bring
> >them up to date with the top of libvirt git.
> >
> >NB: I did send Henning the changes after the fact, but my resend
> >using the same message-id skills so that replies are left in the
> >onlist series are lacking. Henning has looked at the first patch
> >- with a response here:
> >
> >http://www.redhat.com/archives/libvir-list/2016-January/msg00443.html
> >
> >Finally, I think these changes should go into 1.3.1 since that's
> >when the regression was introduced.
> >
>
> It would be nice to have them in, I really tried reviewing them,
> but I can't wrap my head around last two of them. Maybe because
> I'm already late for an appointment I have.
>
> So unfortunately I have to leave you without the review for those
> two as I really need to go, but anyone else feel free to continue.
> And even re-check my reviews for 1 and 2 if you want. It would be
> a pity not to fix a regression when we could.
I agree we need to get these into the next release, but please hold
off from merging them. I want to re-examine Henning's original patches
in more detail, as I have a bad feeling we might need to simply revert
all of them and start again.
Until when do these patches need to be reviewed? The 1/4 is obvious but
the other ones need a closer look. I can just say that they do not seem
right.
I pulled virCgroupAddTask out of virCgroupNewMachine* and that should
be done. But it seems to me that the way virCgroupAddTask was called
contained important error handling that should remain in
virCgroupNewMachine.
If we only have a couple of days to the next release i would suggest
reverting my changes to give us time to figure the whole thing out.
I will have limited time to look into that until the end of the month.
But i certainly want those changes merged, or something that helps
solve/mitigate the realtime problems of the current implementation. My
changes address only a fraction of the problem. My suggestion for a
proper solution would be using the exclusive flags of cgroups, which
will require a totally different cgroup layout. Something like a
"machine.slice_excl" next to "machine.slice" with the current
structure
replicated in there. Or a "top-level" exclusive cgroup per instance. So
far i only looked at the implications for cpu_exclusive, where such a
setup can work and will properly "protect" the reserved cpus from
accidential use.
Regards,
Henning