Re: [PATCH v4 4/5] lxc: Implement virtual /proc/cpuinfo via LXC fuse

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(a)gmail.com&gt; > --- > 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 -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|