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Re: [libvirt] [PATCH] set cpu bandwidth for the vm



Daniel,

Would you get a chance to take a look at this patch.

Thanks,
Gui

On 2011-7-25 13:37, Wen Congyang wrote:
> The cpu bandwidth is applied at the vcpu group level. We should apply it
> at the vm group level too, because the vm may do heavy I/O, and it will affect
> the other vm.
> 
> We apply cpu bandwidth at the vcpu and the vm group level, so we must ensure
> that max(child_quota) <= parent_quota when we modify cpu bandwidth.
> 
> ---
>  src/qemu/qemu_cgroup.c |   38 ++++++++++-------
>  src/qemu/qemu_driver.c |  103 ++++++++++++++++++++++++++++++++++++-----------
>  2 files changed, 101 insertions(+), 40 deletions(-)
> 
> diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
> index d6e4cbc..2a10bd2 100644
> --- a/src/qemu/qemu_cgroup.c
> +++ b/src/qemu/qemu_cgroup.c
> @@ -435,6 +435,7 @@ int qemuSetupCgroupForVcpu(struct qemud_driver *driver, virDomainObjPtr vm)
>      unsigned int i;
>      unsigned long long period = vm->def->cputune.period;
>      long long quota = vm->def->cputune.quota;
> +    long long vm_quota = 0;
>  
>      if (driver->cgroup == NULL)
>          return 0; /* Not supported, so claim success */
> @@ -447,26 +448,31 @@ int qemuSetupCgroupForVcpu(struct qemud_driver *driver, virDomainObjPtr vm)
>          goto cleanup;
>      }
>  
> +    /* Set cpu bandwidth for the vm */
> +    if (period || quota) {
> +        if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_CPU)) {
> +            /* Ensure that we can multiply by vcpus without overflowing. */
> +            if (quota > LLONG_MAX / vm->def->vcpus) {
> +                virReportSystemError(EINVAL,
> +                                     _("%s"),
> +                                     "Unable to set cpu bandwidth quota");
> +                goto cleanup;
> +            }
> +
> +            if (quota > 0)
> +                vm_quota = quota * vm->def->vcpus;
> +            else
> +                vm_quota = quota;
> +            if (qemuSetupCgroupVcpuBW(cgroup, period, vm_quota) < 0)
> +                goto cleanup;
> +        }
> +    }
> +
>      if (priv->nvcpupids == 0 || priv->vcpupids[0] == vm->pid) {
>          /* If we does not know VCPU<->PID mapping or all vcpu runs in the same
>           * thread, we cannot control each vcpu.
>           */
> -        if (period || quota) {
> -            if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_CPU)) {
> -                /* Ensure that we can multiply by vcpus without overflowing. */
> -                if (quota > LLONG_MAX / vm->def->vcpus) {
> -                    virReportSystemError(EINVAL,
> -                                         _("%s"),
> -                                         "Unable to set cpu bandwidth quota");
> -                    goto cleanup;
> -                }
> -
> -                if (quota > 0)
> -                    quota *= vm->def->vcpus;
> -                if (qemuSetupCgroupVcpuBW(cgroup, period, quota) < 0)
> -                    goto cleanup;
> -            }
> -        }
> +        virCgroupFree(&cgroup);
>          return 0;
>      }
>  
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 5df58b1..52e5d69 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -6051,43 +6051,98 @@ qemuSetVcpusBWLive(virDomainObjPtr vm, virCgroupPtr cgroup,
>      qemuDomainObjPrivatePtr priv = vm->privateData;
>      virCgroupPtr cgroup_vcpu = NULL;
>      int rc;
> +    long long vm_quota = 0;
> +    long long old_quota = 0;
> +    unsigned long long old_period = 0;
>  
>      if (period == 0 && quota == 0)
>          return 0;
>  
> -    if (priv->nvcpupids == 0 || priv->vcpupids[0] == vm->pid) {
> -        /* If we does not know VCPU<->PID mapping or all vcpu runs in the same
> -         * thread, we cannot control each vcpu.
> -         */
> -        /* Ensure that we can multiply by vcpus without overflowing. */
> -        if (quota > LLONG_MAX / vm->def->vcpus) {
> -            virReportSystemError(EINVAL,
> -                                 _("%s"),
> -                                 "Unable to set cpu bandwidth quota");
> -            goto cleanup;
> -        }
> +    /* Ensure that we can multiply by vcpus without overflowing. */
> +    if (quota > LLONG_MAX / vm->def->vcpus) {
> +        virReportSystemError(EINVAL,
> +                             _("%s"),
> +                             "Unable to set cpu bandwidth quota");
> +        goto cleanup;
> +    }
> +
> +    if (quota > 0)
> +        vm_quota = quota * vm->def->vcpus;
> +    else
> +        vm_quota = quota;
>  
> -        if (quota > 0)
> -            quota *= vm->def->vcpus;
> -        return qemuSetupCgroupVcpuBW(cgroup, period, quota);
> +    rc = virCgroupGetCpuCfsQuota(cgroup, &old_quota);
> +    if (rc < 0) {
> +        virReportSystemError(-rc, "%s",
> +                             _("unable to get cpu bandwidth tunable"));
> +        goto cleanup;
>      }
>  
> -    for (i = 0; i < priv->nvcpupids; i++) {
> -        rc = virCgroupForVcpu(cgroup, i, &cgroup_vcpu, 0);
> -        if (rc < 0) {
> -            virReportSystemError(-rc,
> -                                 _("Unable to find vcpu cgroup for %s(vcpu:"
> -                                   " %d)"),
> -                                 vm->def->name, i);
> -            goto cleanup;
> +    rc = virCgroupGetCpuCfsPeriod(cgroup, &old_period);
> +    if (rc < 0) {
> +        virReportSystemError(-rc, "%s",
> +                             _("unable to get cpu bandwidth period tunable"));
> +        goto cleanup;
> +    }
> +
> +    /*
> +     * If quota will be changed to a small value, we should modify vcpu's quota
> +     * first. Otherwise, we should modify vm's quota first.
> +     *
> +     * If period will be changed to a small value, we should modify vm's period
> +     * first. Otherwise, we should modify vcpu's period first.
> +     *
> +     * If both quota and period will be changed to a big/small value, we cannot
> +     * modify period and quota together.
> +     */
> +    if ((quota != 0) && (period != 0)) {
> +        if (((quota > old_quota) && (period > old_period)) ||
> +            ((quota < old_quota) && (period < old_period))) {
> +            /* modify period */
> +            if (qemuSetVcpusBWLive(vm, cgroup, period, 0) < 0)
> +                goto cleanup;
> +
> +            /* modify quota */
> +            if (qemuSetVcpusBWLive(vm, cgroup, 0, quota) < 0)
> +                goto cleanup;
> +            return 0;
>          }
> +    }
>  
> -        if (qemuSetupCgroupVcpuBW(cgroup_vcpu, period, quota) < 0)
> +    if (((vm_quota != 0) && (vm_quota > old_quota)) ||
> +        ((period != 0) && (period < old_period)))
> +        /* Set cpu bandwidth for the vm */
> +        if (qemuSetupCgroupVcpuBW(cgroup, period, vm_quota) < 0)
>              goto cleanup;
>  
> -        virCgroupFree(&cgroup_vcpu);
> +    /* If we does not know VCPU<->PID mapping or all vcpu runs in the same
> +     * thread, we cannot control each vcpu. So we only modify cpu bandwidth
> +     * when each vcpu has a separated thread.
> +     */
> +    if (priv->nvcpupids != 0 && priv->vcpupids[0] != vm->pid) {
> +        for (i = 0; i < priv->nvcpupids; i++) {
> +            rc = virCgroupForVcpu(cgroup, i, &cgroup_vcpu, 0);
> +            if (rc < 0) {
> +                virReportSystemError(-rc,
> +                                     _("Unable to find vcpu cgroup for %s(vcpu:"
> +                                       " %d)"),
> +                                     vm->def->name, i);
> +                goto cleanup;
> +            }
> +
> +            if (qemuSetupCgroupVcpuBW(cgroup_vcpu, period, quota) < 0)
> +                goto cleanup;
> +
> +            virCgroupFree(&cgroup_vcpu);
> +        }
>      }
>  
> +    if (((vm_quota != 0) && (vm_quota <= old_quota)) ||
> +        ((period != 0) && (period >= old_period)))
> +        /* Set cpu bandwidth for the vm */
> +        if (qemuSetupCgroupVcpuBW(cgroup, period, vm_quota) < 0)
> +            goto cleanup;
> +
>      return 0;
>  
>  cleanup:



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