[libvirt] [PATCH 07/17] Add qemuProcessSetHypervisorAffinites and set hypervisor threads affinities

[Hu Tao]

On Mon, Aug 06, 2012 at 05:09:04PM -0600, Eric Blake wrote:
> On 08/03/2012 12:36 AM, Hu Tao wrote:
> > From: Tang Chen <tangchen at cn.fujitsu.com>
> > 
> > Hypervisor threads should also be pinned by sched_setaffinity(), just
> > the same as vcpu threads.
> 
> Indeed, this fallback makes sense when cpuset cgroup is not present.
> 
> Same question as earlier in the series - is affinity necessary when
> cpuset is in effect, or does cpuset already guarantee everything that
> affinity would already provide?
> 
> 
> > +static int
> > +qemuProcessSetHypervisorAffinites(virConnectPtr conn,
> > +                                  virDomainObjPtr vm)
> > +{
> > +    virDomainDefPtr def = vm->def;
> > +    pid_t pid = vm->pid;
> > +    unsigned char *cpumask = NULL;
> > +    unsigned char *cpumap = NULL;
> > +    virNodeInfo nodeinfo;
> > +    int cpumaplen, hostcpus, maxcpu, i;
> > +    int ret = -1;
> > +
> > +    if (virNodeGetInfo(conn, &nodeinfo) != 0)
> > +        return -1;
> > +
> > +    if (!def->cputune.hypervisorpin)
> > +        return 0;
> > +
> > +    hostcpus = VIR_NODEINFO_MAXCPUS(nodeinfo);
> > +    cpumaplen = VIR_CPU_MAPLEN(hostcpus);
> > +    maxcpu = cpumaplen * 8;
> 
> That's a magic number; I prefer CHAR_BIT from <limits.h>.
> 
> Not your fault, but I really hate the amount of gross code duplication
> we have for dealing with conversions between strings, cpu maps, and
> bitmaps.  It would be really nice to scrub the code to make nice helper
> functions that can provide easier conversion interfaces rather than open
> coding the conversion at each client.
> 
> > +
> > +    if (virProcessInfoSetAffinity(pid,
> > +                                  cpumap,
> > +                                  cpumaplen,
> > +                                  maxcpu) < 0) {
> 
> Does this work, or does it slam the affinity of all the vcpu children
> threads at the same time, even when we have used <vcpupin> to request
> different pinning?

Doesn't matter, existing children threads are not affected.



-- 
Thanks,
Hu Tao