Re: [libvirt] [PATCH] qemu: Limit refresh of CPU halted state to s390

On Tue, Feb 06, 2018 at 12:00:31PM +0100, Peter Krempa wrote: > On Tue, Feb 06, 2018 at 11:55:07 +0100, Peter Krempa wrote: > > On Tue, Feb 06, 2018 at 11:18:56 +0100, Viktor Mihajlovski wrote: > > > Refreshing the halted state can cause VM performance issues. Since > > > s390 is currently the only architecture with a known interest in > > > the halted state, we're avoiding to call QEMU on other platforms. > > > > > > Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com&gt; > > > --- > > > src/qemu/qemu_domain.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c > > > index df433c2..d2c833f 100644 > > > --- a/src/qemu/qemu_domain.c > > > +++ b/src/qemu/qemu_domain.c > > > @@ -8634,6 +8634,10 @@ qemuDomainRefreshVcpuHalted(virQEMUDriverPtr driver, > > > if (vm->def->virtType == VIR_DOMAIN_VIRT_QEMU) > > > return 0; > > > > > > + /* Only supported on s390(x) */ > > This would also benefit from a more thorough comment. > > > > + if (!ARCH_IS_S390(vm->def->os.arch)) > > > + return 0; > > > > I think we also should remove the 'halted' field from the stats output > > if the information was not gathered at all, since it would falsely reply > > that the cpu is not halted all the time. > > Also to do so you'll probably need to convert the 'halted' bool to a > tristate, so that the logic determining whether the field should be used > or not is not present in the stats code but it's in the refresh code as > you've added it. Or the lazy way out is to just add ARCH_IS_S390() check in the stats method too