[libvirt] [PATCH v5 4/5] qemu: Add support to pin IOThreads to specific CPU

John Ferlan jferlan at redhat.com
Mon Mar 9 22:53:33 UTC 2015



On 03/09/2015 04:42 PM, Pavel Hrdina wrote:
> On Fri, Mar 06, 2015 at 09:05:44AM -0500, John Ferlan wrote:
>> Add qemuDomainPinIOThread to handle setting the CPU affinity
>> for a specific IOThread
>>
>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>> ---
>>  include/libvirt/libvirt-domain.h |   9 ++
>>  src/qemu/qemu_driver.c           | 221 +++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 230 insertions(+)
>>
> 
> [...]
> 
>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>> index b37474f..aad08b2 100644
>> --- a/src/qemu/qemu_driver.c
>> +++ b/src/qemu/qemu_driver.c
>> @@ -5780,6 +5780,226 @@ qemuDomainGetIOThreadsInfo(virDomainPtr dom,
>>      return ret;
>>  }
>>  
>> +static int
>> +qemuDomainPinIOThread(virDomainPtr dom,
>> +                      unsigned int iothread_id,
>> +                      unsigned char *cpumap,
>> +                      int maplen,
>> +                      unsigned int flags)
>> +{
>> +    int ret = -1;
>> +    virQEMUDriverPtr driver = dom->conn->privateData;
>> +    virQEMUDriverConfigPtr cfg = NULL;
>> +    virDomainObjPtr vm;
>> +    virCapsPtr caps = NULL;
>> +    virDomainDefPtr persistentDef = NULL;
>> +    virBitmapPtr pcpumap = NULL;
>> +    bool doReset = false;
>> +    qemuDomainObjPrivatePtr priv;
>> +    virDomainVcpuPinDefPtr *newIOThreadsPin = NULL;
>> +    size_t newIOThreadsPinNum = 0;
>> +    virCgroupPtr cgroup_iothread = NULL;
>> +    virObjectEventPtr event = NULL;
>> +    char paramField[VIR_TYPED_PARAM_FIELD_LENGTH] = "";
>> +    char *str = NULL;
>> +    virTypedParameterPtr eventParams = NULL;
>> +    int eventNparams = 0;
>> +    int eventMaxparams = 0;
>> +
>> +    virCheckFlags(VIR_DOMAIN_AFFECT_LIVE |
>> +                  VIR_DOMAIN_AFFECT_CONFIG, -1);
>> +
>> +    cfg = virQEMUDriverGetConfig(driver);
>> +
>> +    if (!(vm = qemuDomObjFromDomain(dom)))
>> +        goto cleanup;
>> +    priv = vm->privateData;
>> +
>> +    if (virDomainPinIOThreadEnsureACL(dom->conn, vm->def, flags) < 0)
>> +        goto cleanup;
>> +
>> +    if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
>> +        goto cleanup;
>> +
>> +    if (vm->def->placement_mode == VIR_DOMAIN_CPU_PLACEMENT_MODE_AUTO) {
>> +        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
>> +                       _("Changing affinity for IOThread dynamically is "
>> +                         "not allowed when CPU placement is 'auto'"));
>> +        goto cleanup;
>> +    }
>> +
>> +    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
>> +        goto cleanup;
>> +
>> +    if (virDomainLiveConfigHelperMethod(caps, driver->xmlopt, vm, &flags,
>> +                                        &persistentDef) < 0)
>> +        goto endjob;
>> +
>> +    if (flags & VIR_DOMAIN_AFFECT_LIVE)
>> +        persistentDef = vm->def;
> 
> This is wrong and you cannot do that.  Imagine that the live definition is
> already different than the persistent definition.  Just remove those two lines.
> 

Head scratcher - there's something that caused me to do this, but I
forget. In any case, persistentDef isn't used with *_LIVE anyway.

>> +
>> +    /* Coverity didn't realize that targetDef must be set if we got here.  */
>> +    sa_assert(persistentDef);

I'll move this closer to the _CONFIG option like other uses.

>> +
>> +    if (!(pcpumap = virBitmapNewData(cpumap, maplen)))
>> +        goto endjob;
>> +
>> +    if (virBitmapIsAllClear(pcpumap)) {
>> +        virReportError(VIR_ERR_INVALID_ARG, "%s",
>> +                       _("Empty iothread cpumap list for pinning"));
>> +        goto endjob;
>> +    }
>> +
>> +    /* pinning to all physical cpus means resetting,
>> +     * so check if we can reset setting.
>> +     */
>> +    if (virBitmapIsAllSet(pcpumap))
>> +        doReset = true;
>> +
>> +    if (flags & VIR_DOMAIN_AFFECT_LIVE) {
>> +
>> +        if (priv->iothreadpids == NULL) {
>> +            virReportError(VIR_ERR_OPERATION_INVALID,
>> +                           "%s", _("IOThread affinity is not supported"));
>> +            goto endjob;
>> +        }
>> +
>> +        if (iothread_id > priv->niothreadpids) {
>> +            virReportError(VIR_ERR_INVALID_ARG,
>> +                           _("iothread value out of range %d > %d"),
>> +                           iothread_id, priv->niothreadpids);
>> +            goto endjob;
>> +        }
>> +
>> +        if (vm->def->cputune.iothreadspin) {
>> +            /* The VcpuPinDefCopy works for IOThreads too */
>> +            newIOThreadsPin =
>> +                virDomainVcpuPinDefCopy(vm->def->cputune.iothreadspin,
>> +                                        vm->def->cputune.niothreadspin);
>> +            if (!newIOThreadsPin)
>> +                goto endjob;
>> +
>> +            newIOThreadsPinNum = vm->def->cputune.niothreadspin;
>> +        } else {
>> +            if (VIR_ALLOC(newIOThreadsPin) < 0)
>> +                goto endjob;
>> +            newIOThreadsPinNum = 0;
>> +        }
>> +
>> +        if (virDomainIOThreadsPinAdd(&newIOThreadsPin, &newIOThreadsPinNum,
>> +                                     cpumap, maplen, iothread_id) < 0) {
>> +            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                           _("failed to update iothreadspin"));
>> +            virDomainVcpuPinDefArrayFree(newIOThreadsPin, newIOThreadsPinNum);
> 
> This free function needs to be called in cleanup section because we are jumping
> to endjob from several places.
> 

Interesting - the vcpupin will have the same issue...

I'll have to send a followup patch for that though...

Thanks for the reviews.

John

>> +            goto endjob;
>> +        }
>> +
>> +        /* Configure the corresponding cpuset cgroup before set affinity. */
>> +        if (virCgroupHasController(priv->cgroup,
>> +                                   VIR_CGROUP_CONTROLLER_CPUSET)) {
>> +            if (virCgroupNewIOThread(priv->cgroup, iothread_id,
>> +                                     false, &cgroup_iothread) < 0)
>> +                goto endjob;
>> +            if (qemuSetupCgroupIOThreadsPin(cgroup_iothread,
>> +                                            newIOThreadsPin,
>> +                                            newIOThreadsPinNum,
>> +                                            iothread_id) < 0) {
>> +                virReportError(VIR_ERR_OPERATION_INVALID,
>> +                               _("failed to set cpuset.cpus in cgroup"
>> +                                 " for iothread %d"), iothread_id);
>> +                goto endjob;
>> +            }
>> +        } else {
>> +            if (virProcessSetAffinity(priv->iothreadpids[iothread_id - 1],
>> +                                      pcpumap) < 0) {
>> +                virReportError(VIR_ERR_SYSTEM_ERROR,
>> +                               _("failed to set cpu affinity for IOThread %d"),
>> +                               iothread_id);
>> +                goto endjob;
>> +            }
>> +        }
>> +
>> +        if (doReset) {
>> +            virDomainIOThreadsPinDel(vm->def, iothread_id);
>> +        } else {
>> +            if (vm->def->cputune.iothreadspin)
>> +                virDomainVcpuPinDefArrayFree(vm->def->cputune.iothreadspin,
>> +                                             vm->def->cputune.niothreadspin);
>> +
>> +            vm->def->cputune.iothreadspin = newIOThreadsPin;
>> +            vm->def->cputune.niothreadspin = newIOThreadsPinNum;
>> +            newIOThreadsPin = NULL;
>> +        }
>> +
>> +        if (newIOThreadsPin)
>> +            virDomainVcpuPinDefArrayFree(newIOThreadsPin, newIOThreadsPinNum);
> 
> Those two exact lines should be in cleanup section.
> 

It seems it's "safe" to just move them then since this isn't a loop
>> +
>> +        if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0)
>> +            goto endjob;
>> +
>> +        if (snprintf(paramField, VIR_TYPED_PARAM_FIELD_LENGTH,
>> +                     VIR_DOMAIN_TUNABLE_CPU_IOTHREADSPIN, iothread_id) < 0) {
>> +            goto endjob;
>> +        }
>> +
>> +        str = virBitmapFormat(pcpumap);
>> +        if (virTypedParamsAddString(&eventParams, &eventNparams,
>> +                                    &eventMaxparams, paramField, str) < 0)
>> +            goto endjob;
>> +
>> +        event = virDomainEventTunableNewFromDom(dom, eventParams, eventNparams);
>> +    }
>> +
>> +    if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
>> +        if (iothread_id > persistentDef->iothreads) {
>> +            virReportError(VIR_ERR_INVALID_ARG,
>> +                           _("iothread value out of range %d > %d"),
>> +                           iothread_id, persistentDef->iothreads);
>> +            goto endjob;
>> +        }
>> +
>> +        if (doReset) {
>> +            virDomainIOThreadsPinDel(persistentDef, iothread_id);
>> +        } else {
>> +            if (!persistentDef->cputune.iothreadspin) {
>> +                if (VIR_ALLOC(persistentDef->cputune.iothreadspin) < 0)
>> +                    goto endjob;
>> +                persistentDef->cputune.niothreadspin = 0;
>> +            }
>> +            if (virDomainIOThreadsPinAdd(&persistentDef->cputune.iothreadspin,
>> +                                         &persistentDef->cputune.niothreadspin,
>> +                                         cpumap,
>> +                                         maplen,
>> +                                         iothread_id) < 0) {
>> +                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                               _("failed to update or add iothreadspin xml "
>> +                                 "of a persistent domain"));
>> +                goto endjob;
>> +            }
>> +        }
>> +
>> +        ret = virDomainSaveConfig(cfg->configDir, persistentDef);
>> +        goto endjob;
>> +    }
>> +
>> +    ret = 0;
>> +
>> + endjob:
>> +    qemuDomainObjEndJob(driver, vm);
>> +
>> + cleanup:
>> +    if (cgroup_iothread)
>> +        virCgroupFree(&cgroup_iothread);
>> +    if (event)
>> +        qemuDomainEventQueue(driver, event);
>> +    VIR_FREE(str);
>> +    virBitmapFree(pcpumap);
>> +    qemuDomObjEndAPI(&vm);
>> +    virObjectUnref(caps);
>> +    virObjectUnref(cfg);
>> +    return ret;
>> +}
>> +
>>  static int qemuDomainGetSecurityLabel(virDomainPtr dom, virSecurityLabelPtr seclabel)
>>  {
>>      virQEMUDriverPtr driver = dom->conn->privateData;
>> @@ -19328,6 +19548,7 @@ static virHypervisorDriver qemuHypervisorDriver = {
>>      .domainGetVcpus = qemuDomainGetVcpus, /* 0.4.4 */
>>      .domainGetMaxVcpus = qemuDomainGetMaxVcpus, /* 0.4.4 */
>>      .domainGetIOThreadsInfo = qemuDomainGetIOThreadsInfo, /* 1.2.14 */
>> +    .domainPinIOThread = qemuDomainPinIOThread, /* 1.2.14 */
>>      .domainGetSecurityLabel = qemuDomainGetSecurityLabel, /* 0.6.1 */
>>      .domainGetSecurityLabelList = qemuDomainGetSecurityLabelList, /* 0.10.0 */
>>      .nodeGetSecurityModel = qemuNodeGetSecurityModel, /* 0.6.1 */
>> -- 
>> 2.1.0
>>
> 
> Otherwise looks good.  ACK with the fixes mentioned above.
> 
> Pavel
> 




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