Thanks for your comments, Daniel.
Well, since you have a consensus about /proc/cpuinfo, I will only
resubmit the patches related to timer.
Julio Cesar Faracco
Em ter., 25 de fev. de 2020 às 08:34, Daniel P. Berrangé
<berrange@xxxxxxxxxx> escreveu:
>
> On Mon, Feb 24, 2020 at 11:24:28AM -0300, Julio Faracco wrote:
> > This commit tries to fix lots of issues related to LXC VCPUs. One of
> > them is related to /proc/cpuinfo content. If only 1 VCPU is set, LXC
> > containers will show all CPUs available for host. The second one is
> > related to CPU share, if an user set only 1 VCPU, the container/process
> > will use all available CPUs. (This is not the case when `cpuset`
> > attribute is declared). So, this commit adds a virtual cpuinfo based on
> > VCPU mapping and it automatically limits the CPU usage according VCPU
> > count.
> >
> > Example (now):
> > LXC container - 8 CPUS with 2 VCPU:
> > lxc-root# stress --cpu 8
> >
> > On host machine, only CPU 0 and 1 have 100% usage.
> >
> > Signed-off-by: Julio Faracco <jcfaracco@xxxxxxxxx>
> > ---
> > src/lxc/lxc_cgroup.c | 31 ++++++++++++++
> > src/lxc/lxc_container.c | 39 ++++++++++-------
> > src/lxc/lxc_fuse.c | 95 ++++++++++++++++++++++++++++++++++++++---
> > 3 files changed, 145 insertions(+), 20 deletions(-)
> >
> > diff --git a/src/lxc/lxc_cgroup.c b/src/lxc/lxc_cgroup.c
> > index d29b65092a..912a252473 100644
> > --- a/src/lxc/lxc_cgroup.c
> > +++ b/src/lxc/lxc_cgroup.c
> > @@ -50,6 +50,34 @@ static int virLXCCgroupSetupCpuTune(virDomainDefPtr def,
> > }
> >
> >
> > +static int virLXCCgroupSetupVcpuAuto(virDomainDefPtr def,
> > + virCgroupPtr cgroup)
> > +{
> > + size_t i;
> > + int vcpumax;
> > + virBuffer buffer = VIR_BUFFER_INITIALIZER;
> > + virBufferPtr cpuset = &buffer;
> > +
> > + vcpumax = virDomainDefGetVcpusMax(def);
> > + for (i = 0; i < vcpumax; i++) {
> > + virDomainVcpuDefPtr vcpu = virDomainDefGetVcpu(def, i);
> > + /* Cgroup is smart enough to convert numbers separated
> > + * by comma into ranges. Example: "0,1,2,5," -> "0-2,5".
> > + * Libvirt does not need to process it here. */
> > + if (vcpu)
> > + virBufferAsprintf(cpuset, "%zu,", i);
> > + }
>
> If I have 4 containers, each with vcpu==2, then all 4 containers
> are going to be taskset onto host CPUs 0 & 1, and host CPUs 2,3,4,5,6,7
> are going to be unused. This is not viable as a strategy.
>
> > + if (virCgroupSetCpusetCpus(cgroup,
> > + virBufferCurrentContent(cpuset)) < 0) {
> > + virBufferFreeAndReset(cpuset);
> > + return -1;
> > + }
> > +
> > + virBufferFreeAndReset(cpuset);
> > + return 0;
> > +}
>
> > +static int
> > +lxcProcReadCpuinfoParse(virDomainDefPtr def, char *base,
> > + virBufferPtr new_cpuinfo)
> > +{
> > + char *procline = NULL;
> > + char *saveptr = base;
> > + size_t cpu;
> > + size_t nvcpu;
> > + size_t curcpu = 0;
> > + bool get_proc = false;
> > +
> > + nvcpu = virDomainDefGetVcpus(def);
> > + while ((procline = strtok_r(NULL, "\n", &saveptr))) {
> > + if (sscanf(procline, "processor\t: %zu", &cpu) == 1) {
>
> This doesn't work because it is assuming the /proc/cpuinfo data format
> for x86 architecture. Every architecture puts different info in this
> file, and only some of them using "processor: NN" as a delimiter for
> new entries. There's many examples in tests/sysinfodata/ and
> in tests/virhostcpudata/ showing this problem
>
> We had considered taking /proc/cpuinfo in the past, but decided against
> it. Since this file is non-standard data format varying across arches,
> well written apps won't actually look at /proc/cpuinfo at all. Instead
> they'll use /sys/devices/system/cpu instead. I don't think we want to
> make /proc/cpuinfo be inconsistent with data in sysfs.
>
>
> > + virDomainVcpuDefPtr vcpu = virDomainDefGetVcpu(def, cpu);
> > + /* VCPU is mapped */
> > + if (vcpu) {
> > + if (curcpu == nvcpu)
> > + break;
> > +
> > + if (curcpu > 0)
> > + virBufferAddLit(new_cpuinfo, "\n");
> > +
> > + virBufferAsprintf(new_cpuinfo, "processor\t: %zu\n",
> > + curcpu);
> > + curcpu++;
> > + get_proc = true;
> > + } else {
> > + get_proc = false;
> > + }
> > + } else {
> > + /* It is not a processor index */
> > + if (get_proc)
> > + virBufferAsprintf(new_cpuinfo, "%s\n", procline);
> > + }
> > + }
> > +
> > + virBufferAddLit(new_cpuinfo, "\n");
> > +
> > + return strlen(virBufferCurrentContent(new_cpuinfo));
> > +}
>
> Regards,
> Daniel
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