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Re: [libvirt] [PATCHv5 2/2] Adds support to param 'vcpu_time' in qemu_driver.



On Thu, May 17, 2012 at 03:56:48PM -0600, Eric Blake wrote:
> From: Hu Tao <hutao cn fujitsu com>
> 
> This involves setting the cpuacct cgroup to a per-vcpu granularity,
> as well as summing the each vcpu accounting into a common array.
> Now that we are reading more than one cgroup file, we double-check
> that cpus weren't hot-plugged between reads to invalidate our
> summing.
> 
> Signed-off-by: Eric Blake <eblake redhat com>
> ---
> 
> diff from v4: rewrite qemu code to use fewer malloc calls, fix
> some logic bugs
> 
>  src/qemu/qemu_driver.c |  123 ++++++++++++++++++++++++++++++++++++++++++++----
>  src/util/cgroup.c      |    4 +-
>  2 files changed, 117 insertions(+), 10 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 0fd7de1..f6d0985 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -104,7 +104,7 @@
>  #define QEMU_NB_NUMA_PARAM 2
> 
>  #define QEMU_NB_TOTAL_CPU_STAT_PARAM 3
> -#define QEMU_NB_PER_CPU_STAT_PARAM 1
> +#define QEMU_NB_PER_CPU_STAT_PARAM 2
> 
>  #if HAVE_LINUX_KVM_H
>  # include <linux/kvm.h>
> @@ -12563,8 +12563,69 @@ qemuDomainGetTotalcpuStats(virCgroupPtr group,
>      return nparams;
>  }
> 
> +/* This function gets the sums of cpu time consumed by all vcpus.
> + * For example, if there are 4 physical cpus, and 2 vcpus in a domain,
> + * then for each vcpu, the cpuacct.usage_percpu looks like this:
> + *   t0 t1 t2 t3
> + * and we have 2 groups of such data:
> + *   v\p   0   1   2   3
> + *   0   t00 t01 t02 t03
> + *   1   t10 t11 t12 t13
> + * for each pcpu, the sum is cpu time consumed by all vcpus.
> + *   s0 = t00 + t10
> + *   s1 = t01 + t11
> + *   s2 = t02 + t12
> + *   s3 = t03 + t13
> + */
> +static int
> +getSumVcpuPercpuStats(virCgroupPtr group,
> +                      unsigned int nvcpu,
> +                      unsigned long long *sum_cpu_time,
> +                      unsigned int num)
> +{
> +    int ret = -1;
> +    int i;
> +    char *buf = NULL;
> +    virCgroupPtr group_vcpu = NULL;
> +
> +    for (i = 0; i < nvcpu; i++) {
> +        char *pos;
> +        unsigned long long tmp;
> +        int j;
> +
> +        if (virCgroupForVcpu(group, i, &group_vcpu, 0) < 0) {
> +            qemuReportError(VIR_ERR_INTERNAL_ERROR,
> +                            _("error accessing cgroup cpuacct for vcpu"));
> +            goto cleanup;
> +        }
> +
> +        if (virCgroupGetCpuacctPercpuUsage(group, &buf) < 0)
> +            goto cleanup;
> +
> +        pos = buf;
> +        for (j = 0; j < num; j++) {
> +            if (virStrToLong_ull(pos, &pos, 10, &tmp) < 0) {
> +                qemuReportError(VIR_ERR_INTERNAL_ERROR,
> +                                _("cpuacct parse error"));
> +                goto cleanup;
> +            }
> +            sum_cpu_time[j] += tmp;
> +        }
> +
> +        virCgroupFree(&group_vcpu);
> +        VIR_FREE(buf);
> +    }
> +
> +    ret = 0;
> +cleanup:
> +    virCgroupFree(&group_vcpu);
> +    VIR_FREE(buf);
> +    return ret;
> +}
> +
>  static int
>  qemuDomainGetPercpuStats(virDomainPtr domain,
> +                         virDomainObjPtr vm,
>                           virCgroupPtr group,
>                           virTypedParameterPtr params,
>                           unsigned int nparams,
> @@ -12572,20 +12633,24 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
>                           unsigned int ncpus)
>  {
>      char *map = NULL;
> +    char *map2 = NULL;
>      int rv = -1;
>      int i, max_id;
>      char *pos;
>      char *buf = NULL;
> +    unsigned long long *sum_cpu_time = NULL;
> +    unsigned long long *sum_cpu_pos;
> +    unsigned int n = 0;
> +    qemuDomainObjPrivatePtr priv = vm->privateData;
>      virTypedParameterPtr ent;
>      int param_idx;
> +    unsigned long long cpu_time;
> 
>      /* return the number of supported params */
>      if (nparams == 0 && ncpus != 0)
> -        return QEMU_NB_PER_CPU_STAT_PARAM; /* only cpu_time is supported */
> +        return QEMU_NB_PER_CPU_STAT_PARAM;
> 
> -    /* return percpu cputime in index 0 */
> -    param_idx = 0;
> -    /* to parse account file, we need "present" cpu map */
> +    /* To parse account file, we need "present" cpu map.  */
>      map = nodeGetCPUmap(domain->conn, &max_id, "present");
>      if (!map)
>          return rv;
> @@ -12608,30 +12673,70 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
>      pos = buf;
>      memset(params, 0, nparams * ncpus);
> 
> +    /* return percpu cputime in index 0 */
> +    param_idx = 0;
> +
>      if (max_id - start_cpu > ncpus - 1)
>          max_id = start_cpu + ncpus - 1;
> 
>      for (i = 0; i <= max_id; i++) {
> -        unsigned long long cpu_time;
> -
>          if (!map[i]) {
>              cpu_time = 0;
>          } else if (virStrToLong_ull(pos, &pos, 10, &cpu_time) < 0) {
>              qemuReportError(VIR_ERR_INTERNAL_ERROR,
>                              _("cpuacct parse error"));
>              goto cleanup;
> +        } else {
> +            n++;
>          }
>          if (i < start_cpu)
>              continue;
> -        ent = &params[ (i - start_cpu) * nparams + param_idx];
> +        ent = &params[(i - start_cpu) * nparams + param_idx];
>          if (virTypedParameterAssign(ent, VIR_DOMAIN_CPU_STATS_CPUTIME,
>                                      VIR_TYPED_PARAM_ULLONG, cpu_time) < 0)
>              goto cleanup;
>      }
> +
> +    /* return percpu vcputime in index 1 */
> +    if (++param_idx >= nparams) {
> +        rv = nparams;
> +        goto cleanup;
> +    }
> +
> +    if (VIR_ALLOC_N(sum_cpu_time, n) < 0) {
> +        virReportOOMError();
> +        goto cleanup;
> +    }
> +    if (getSumVcpuPercpuStats(group, priv->nvcpupids, sum_cpu_time, n) < 0)
> +        goto cleanup;
> +
> +    /* Check that the mapping of online cpus didn't change mid-parse.  */
> +    map2 = nodeGetCPUmap(domain->conn, &max_id, "present");
> +    if (!map2 || memcmp(map, map2, VIR_DOMAIN_CPUMASK_LEN) != 0)
> +        goto cleanup;
> +
> +    sum_cpu_pos = sum_cpu_time;
> +    for (i = 0; i <= max_id; i++) {
> +        if (!map[i])
> +            cpu_time = 0;
> +        else
> +            cpu_time = *(sum_cpu_pos++);
> +        if (i < start_cpu)
> +            continue;
> +        if (virTypedParameterAssign(&params[(i - start_cpu) * nparams +
> +                                            param_idx],
> +                                    VIR_DOMAIN_CPU_STATS_VCPUTIME,
> +                                    VIR_TYPED_PARAM_ULLONG,
> +                                    cpu_time) < 0)
> +            goto cleanup;
> +    }
> +
>      rv = param_idx + 1;
>  cleanup:
> +    VIR_FREE(sum_cpu_time);
>      VIR_FREE(buf);
>      VIR_FREE(map);
> +    VIR_FREE(map2);
>      return rv;
>  }
> 
> @@ -12683,7 +12788,7 @@ qemuDomainGetCPUStats(virDomainPtr domain,
>      if (start_cpu == -1)
>          ret = qemuDomainGetTotalcpuStats(group, params, nparams);
>      else
> -        ret = qemuDomainGetPercpuStats(domain, group, params, nparams,
> +        ret = qemuDomainGetPercpuStats(domain, vm, group, params, nparams,
>                                         start_cpu, ncpus);
>  cleanup:
>      virCgroupFree(&group);
> diff --git a/src/util/cgroup.c b/src/util/cgroup.c
> index ad49bc2..5b32881 100644
> --- a/src/util/cgroup.c
> +++ b/src/util/cgroup.c
> @@ -530,7 +530,9 @@ static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group,
>              continue;
> 
>          /* We need to control cpu bandwidth for each vcpu now */
> -        if ((flags & VIR_CGROUP_VCPU) && (i != VIR_CGROUP_CONTROLLER_CPU)) {
> +        if ((flags & VIR_CGROUP_VCPU) &&
> +            (i != VIR_CGROUP_CONTROLLER_CPU &&
> +             i != VIR_CGROUP_CONTROLLER_CPUACCT)) {
>              /* treat it as unmounted and we can use virCgroupAddTask */
>              VIR_FREE(group->controllers[i].mountPoint);
>              continue;
> -- 
> 1.7.7.6

ACK.

-- 
Thanks,
Hu Tao


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