[libvirt][PATCH v1 1/1] introduce an attribute "migratable" to numatune memory element
Zhong, Luyao
luyao.zhong at intel.com
Wed Oct 14 05:49:14 UTC 2020
On 10/6/2020 3:15 PM, Peter Krempa wrote:
> On Tue, Oct 06, 2020 at 13:47:25 +0800, Luyao Zhong wrote:
>> <numatune>
>> <memory mode="strict" nodeset="1-4,^3" migratable="yes/no" />
>> <memnode cellid="0" mode="strict" nodeset="1"/>
>> <memnode cellid="2" mode="preferred" nodeset="2"/>
>> </numatune>
>>
>> Attribute ``migratable`` will be 'no' by default, and 'yes' indicates
>> that it allows operating system or hypervisor migrating the memory
>> pages between different memory nodes, that also means we will not
>> rely on hypervisor to set the memory policy or memory affinity, we only
>> use cgroups to restrict the memory nodes, so if ``migratable`` is 'yes',
>> the ``mode`` which indicates memory policy will be ignored.
>
> Note that I'm not reviewing whether this is justified and makes sense.
> I'm commenting purely on the code.
>
>> ---
> We require that patches are split into logical blocks. You need to split
> this commit at least into following patches:
>> docs/formatdomain.rst | 8 +++-
>> docs/schemas/domaincommon.rng | 5 +++
>> src/conf/numa_conf.c | 45 +++++++++++++++++++
>> src/conf/numa_conf.h | 3 ++
>> src/libvirt_private.syms | 1 +
>
> Docs, schema and parser changes should be separated
Got it.
>
>> src/qemu/qemu_command.c | 6 ++-
>> src/qemu/qemu_process.c | 21 +++++++++
>> .../numatune-memory-migratable.args | 34 ++++++++++++++
>> .../numatune-memory-migratable.err | 1 +
>> .../numatune-memory-migratable.xml | 33 ++++++++++++++
>> tests/qemuxml2argvtest.c | 5 +++
>
> Implementation in qemu can be all together with tests. Please also add a
> qemuxml2xmltest case.
>
> I've provided some more feedback in a recent review:
>
> https://www.redhat.com/archives/libvir-list/2020-October/msg00231.html
>
> specifically some guidance on tests:
>
> https://www.redhat.com/archives/libvir-list/2020-October/msg00395.html
>
Got it. Thanks.
>
>> 11 files changed, 160 insertions(+), 2 deletions(-)
>> create mode 100644 tests/qemuxml2argvdata/numatune-memory-migratable.args
>> create mode 100644 tests/qemuxml2argvdata/numatune-memory-migratable.err
>> create mode 100644 tests/qemuxml2argvdata/numatune-memory-migratable.xml
>>
>> diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
>> index cc4f91d4ea..4e386a0c3d 100644
>> --- a/docs/formatdomain.rst
>> +++ b/docs/formatdomain.rst
>
> [...]
>
>> @@ -1097,6 +1097,12 @@ NUMA Node Tuning
>> will be ignored if it's specified. If ``placement`` of ``vcpu`` is 'auto',
>> and ``numatune`` is not specified, a default ``numatune`` with ``placement``
>> 'auto' and ``mode`` 'strict' will be added implicitly. :since:`Since 0.9.3`
>> + Attribute ``migratable`` is 'no' by default, and 'yes' indicates that it
>> + allows operating system or hypervisor migrating the memory pages between
>> + different memory nodes, that also means we will not rely on hypervisor to
>> + set the memory policy or memory affinity, we only use cgroups to restrict
>> + the memory nodes, so if ``migratable`` is 'yes', the ``mode`` which indicates
>> + memory policy will be ignored.
>
> So ... does this make us ignore the per NUMA-node set 'mode'? If yes,
> the code should actually reject any configs where we ignore some
> settings rather than just relying on the docs.
>
Yes, it will ignore the per NUMA-node set 'mode'. So let me saying in
this way, if 'migratable' is set, per NUMA-node mode should not be set,
otherwise the config will be rejected, so the mode will have 'None' as
its default value but not 'strict'.
>
>> ``memnode``
>> Optional ``memnode`` elements can specify memory allocation policies per each
>> guest NUMA node. For those nodes having no corresponding ``memnode`` element,
>
> [...]
>
>> diff --git a/src/conf/numa_conf.c b/src/conf/numa_conf.c
>> index 6653ba05a6..c14ba1295c 100644
>> --- a/src/conf/numa_conf.c
>> +++ b/src/conf/numa_conf.c
>
> [...]
>
>> @@ -292,6 +294,15 @@ virDomainNumatuneParseXML(virDomainNumaPtr numa,
>> placement = VIR_DOMAIN_NUMATUNE_PLACEMENT_AUTO;
>>
>> if (node) {
>> + if ((tmp = virXMLPropString(node, "migratable")) &&
>> + (migratable = virTristateBoolTypeFromString(tmp)) <= 0) {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>
> VIR_ERR_XML_ERROR
Got it.
>
>> + _("Invalid 'migratable' attribute value '%s'"), tmp);
>> + goto cleanup;
>> + }
>> + numa->memory.migratable = migratable;
>> + VIR_FREE(tmp);
>> +
>> if ((tmp = virXMLPropString(node, "mode")) &&
>> (mode = virDomainNumatuneMemModeTypeFromString(tmp)) < 0) {
>> virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> @@ -369,6 +380,11 @@ virDomainNumatuneFormatXML(virBufferPtr buf,
>> tmp = virDomainNumatuneMemModeTypeToString(numatune->memory.mode);
>> virBufferAsprintf(buf, "<memory mode='%s' ", tmp);
>>
>> + if (numatune->memory.migratable) {
>
> Use an explicit condition here:
>
> if (numatune->memory.migratable != VIR_TRISTATE_BOOL_ABSENT)
>
Got it.
>> + tmp = virTristateBoolTypeToString(numatune->memory.migratable);
>> + virBufferAsprintf(buf, "migratable='%s' ", tmp);
>> + }
>> +
>> if (numatune->memory.placement == VIR_DOMAIN_NUMATUNE_PLACEMENT_STATIC) {
>> if (!(nodeset = virBitmapFormat(numatune->memory.nodeset)))
>> return -1;
>> @@ -427,6 +443,35 @@ virDomainNumaFree(virDomainNumaPtr numa)
>> VIR_FREE(numa);
>> }
>>
>> +/**
>> + * virDomainNumatuneGetMigratable:
>> + * @numatune: pointer to numatune definition
>> + * @migratable: where to store the result
>
> This argument is not used by the only place calling it. Please remove
> it.
>
Got it.
>> + *
>> + * Get the migratable attribute for domain's memory. It's safe to
>> + * pass NULL to @migratable if the return value is the only info needed.
>
>> + *
>> + * Returns: migratable value
>> + */
>> +int virDomainNumatuneGetMigratable(virDomainNumaPtr numatune,
>> + virTristateBool *migratable)
>> +{
>> + virTristateBool tmp_migratable = 0;
>> +
>> + if (!numatune)
>> + return tmp_migratable;
>
> Just directly return VIR_TRISTATE_BOOL_ABSENT here ...
>
Got it.
>> +
>> + if (numatune->memory.specified)
>> + tmp_migratable = numatune->memory.migratable;
>> + else
>> + return tmp_migratable;
>> +
>> + if (migratable != NULL)
>> + *migratable = tmp_migratable;
>
>
> Also none of this is really needed, just directly return the value.
>
Got it.
>> +
>> + return tmp_migratable;
>> +}
>> +
>> /**
>> * virDomainNumatuneGetMode:
>> * @numatune: pointer to numatune definition
>
> [...]
>
>> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>> index 476cf6972e..882e7e6ba2 100644
>> --- a/src/qemu/qemu_command.c
>> +++ b/src/qemu/qemu_command.c
>> @@ -3189,7 +3189,11 @@ qemuBuildMemoryBackendProps(virJSONValuePtr *backendProps,
>> return -1;
>> }
>>
>> - if (nodemask) {
>> + // If migratable attribute is yes, we should only use cgroups setting
>> + // memory affinity, and skip passing the host-nodes and policy parameters
>> + // to QEMU command line.
>
> We don't use line comments ('//') in our code base. Please use block
> comments.
>
Got it.
>> + if (nodemask &&
>> + virDomainNumatuneGetMigratable(def->numa, NULL) != VIR_TRISTATE_BOOL_YES) {
>> if (!virNumaNodesetIsAvailable(nodemask))
>> return -1;
>> if (virJSONValueObjectAdd(props,
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index 6b5de29fdb..9c1116064b 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>
> [...]
>
>> @@ -2694,6 +2695,26 @@ qemuProcessSetupPid(virDomainObjPtr vm,
>> &mem_mask, -1) < 0)
>> goto cleanup;
>>
>> + // For vCPU threads, mem_mask is different among cells
>> + if (nameval == VIR_CGROUP_THREAD_VCPU) {
>> + virDomainNumaPtr numatune = vm->def->numa;
>> + virBitmapPtr numanode_cpumask = NULL;
>> + for (i = 0; i < virDomainNumaGetNodeCount(numatune); i++) {
>> + numanode_cpumask = virDomainNumaGetNodeCpumask(numatune, i);
>> + // 'i' indicates the cell id, if the vCPU id is in this cell,
>> + // we need get the corresonding nodeset
>> + if (virBitmapIsBitSet(numanode_cpumask, id)) {
>> + if (virDomainNumatuneMaybeFormatNodeset(numatune,
>> + priv->autoNodeset,
>> + &mem_mask, i) < 0) {
>> + goto cleanup;
>> + } else {
>> + break;
>> + }
>> + }
>> + }
>> + }
>
> This hunk doesn't seem to belong to this patch. The comments (apart from
> using wrong syntax) don't seem to justify why or how this relates to
> memory migrability.
>
It relates to migrability.
<numatune>
<memory mode="strict" nodeset="1-2", migratable='yes'/>
<memnode cellid="0" nodeset="1"/>
<memnode cellid="2" nodeset="2"/>
</numatune>
originally, it will set "1-2" to cgroups cpuset.mems for all vcpus,
but acctually, we should set '1' for vcpus in cell 0, set '2' for vcpus
in cell 2, and set '1-2' for vcpus in other cells.
cgroups can ristrict the memory allocation of the thread at the
beginning, and allow the memory page migrability of the operate system
or hypervisor.
I'll make it clear in comment.
>> +
>> if (virCgroupNewThread(priv->cgroup, nameval, id, true, &cgroup) < 0)
>> goto cleanup;
>>
>
> [...]
>
>> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
>> index 49567326d4..e6554518d7 100644
>> --- a/tests/qemuxml2argvtest.c
>> +++ b/tests/qemuxml2argvtest.c
>> @@ -1950,6 +1950,11 @@ mymain(void)
>>
>> DO_TEST("numatune-memory", NONE);
>> DO_TEST_PARSE_ERROR("numatune-memory-invalid-nodeset", NONE);
>> + DO_TEST("numatune-memory-migratable",
>> + QEMU_CAPS_NUMA,
>> + QEMU_CAPS_OBJECT_MEMORY_RAM);
>> + DO_TEST_PARSE_ERROR("numatune-memory-migratable", NONE);
>
> Pleased don't use DO_TEST any more. Use DO_TEST_CAPS_* (such as
> DO_TEST_CAPS_LATEST) instead for new tests.
>
> The negative test doesn't seem to make sense here since it's not testing
> a negative case in your patch. This is visible from the error message it
> records:
>
Got it.
> > +++ b/tests/qemuxml2argvdata/numatune-memory-migratable.err
> > @@ -0,0 +1 @@
> > +unsupported configuration: Per-node memory binding is not supported with this QEMU
>
Thanks for your review, Peter.
Regards,
Luyao
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