QEMU 2.9.0 will introduce polling feature for AioContext that instead
of blocking syscalls polls for events without blocking. This means
that polling can be in most cases faster but it also increases CPU
utilization.
To address this issue QEMU implements self-tuning algorithm that
modifies the current polling time to adapt to different workloads
and it can also fallback to blocking syscalls.
For each IOThread this all is controlled by three parameters,
poll-max-ns, poll-grow and poll-shrink. If parameter poll-max-ns
is set to 0 it disables the polling, if it is omitted the default
behavior is used and any value more than 0 enables polling.
Parameters poll-grow and poll-shrink configure how the self-tuning
algorithm will adapt the current polling time. If they are omitted
or set to 0 default values will be used.
Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
---
docs/formatdomain.html.in | 19 ++-
docs/schemas/domaincommon.rng | 24 +++
src/conf/domain_conf.c | 169 ++++++++++++++++++++-
src/conf/domain_conf.h | 8 +
src/libvirt_private.syms | 1 +
.../generic-iothreads-no-polling.xml | 22 +++
.../generic-iothreads-polling-disabled.xml | 24 +++
.../generic-iothreads-polling-enabled-fail.xml | 24 +++
.../generic-iothreads-polling-enabled.xml | 24 +++
tests/genericxml2xmltest.c | 6 +
tests/testutils.c | 3 +-
11 files changed, 318 insertions(+), 6 deletions(-)
create mode 100644 tests/genericxml2xmlindata/generic-iothreads-no-polling.xml
create mode 100644 tests/genericxml2xmlindata/generic-iothreads-polling-disabled.xml
create mode 100644 tests/genericxml2xmlindata/generic-iothreads-polling-enabled-fail.xml
create mode 100644 tests/genericxml2xmlindata/generic-iothreads-polling-enabled.xml
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index b69bd4c44c..f01a11cf93 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -611,6 +611,7 @@
...
<iothreadids>
<iothread id="2"/>
+ <polling enabled='yes' max_ns="4000" grow="2" shrink="4"/>
<iothread id="4"/>
<iothread id="6"/>
<iothread id="8"/>
@@ -645,7 +646,23 @@
defined for the domain, then the <code>iothreads</code> value
will be adjusted accordingly.
<span class="since">Since 1.2.15</span>
- </dd>
+ </dd>
+ <dt><code>polling</code></dt>
+ <dd>
+ The optional <code>polling</code> element provides the capability to
+ enable/disable and configure polling mechanism for iothreads. Attribute
+ <code>max_ns</code> specifies the maximum time in <code>ns</code>
+ between each poll requests and is mandatory if polling is explicitly
+ enabled. Attributes <code>grow</code> and <code>shrink</code> specifies
+ time in <code>ns</code> that is used to configure how the polling
+ algorithm will adapt current polling time to different workloads.
+ If any of <code>max_ns</code>, <code>grow</code> and <code>shrink</code>
+ is set to <code>0</code>, it is the same as not providing it at all.
+ If this element is omitted the default behavior and values are set by
+ hypervisor. Possible values for <code>enabled</code> are
+ <code>yes</code> and <code>no</code>. Available only for QEMU driver.
+ <span class="since">Since 3.1.0</span>
+ </dd>
</dl>
<h3><a name="elementsCPUTuning">CPU Tuning</a></h3>
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index c5f101325e..11aecbaa6e 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -661,6 +661,30 @@
<attribute name="id">
<ref name="unsignedInt"/>
</attribute>
+ <optional>
+ <element name="polling">
+ <optional>
+ <attribute name="enabled">
+ <ref name="virYesNo"/>
+ </attribute>
+ </optional>
+ <optional>
+ <attribute name="max_ns">
+ <ref name="unsignedInt"/>
+ </attribute>
+ </optional>
+ <optional>
+ <attribute name="grow">
+ <ref name="unsignedInt"/>
+ </attribute>
+ </optional>
+ <optional>
+ <attribute name="shrink">
+ <ref name="unsignedInt"/>
+ </attribute>
+ </optional>
+ </element>
+ </optional>
</element>
</zeroOrMore>
</element>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 79bdbdf50c..4b552a9175 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -1228,6 +1228,30 @@ virDomainDeviceDefCheckUnsupportedMemoryDevice(virDomainDeviceDefPtr dev)
}
+/**
+ * virDomainDefCheckUnsupportedIOThreadPolling:
+ * @def: domain definition
+ *
+ * Returns -1 if the domain definition would configure IOThread polling
+ * and reports an error, otherwise returns 0.
+ */
+static int
+virDomainDefCheckUnsupportedIOThreadPolling(virDomainDefPtr def)
+{
+ size_t i;
+
+ for (i = 0; i < def->niothreadids; i++) {
+ if (def->iothreadids[i]->poll_enabled != VIR_TRISTATE_BOOL_ABSENT) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("IOThread polling is not supported by this driver"));
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+
bool virDomainObjTaint(virDomainObjPtr obj,
virDomainTaintFlags taint)
{
@@ -4467,6 +4491,10 @@ virDomainDefPostParseCheckFeatures(virDomainDefPtr def,
return -1;
}
+ if (UNSUPPORTED(VIR_DOMAIN_DEF_FEATURE_IOTHREAD_POLLING) &&
+ virDomainDefCheckUnsupportedIOThreadPolling(def) < 0)
+ return -1;
+
return 0;
}
@@ -4585,6 +4613,60 @@ virDomainVcpuDefPostParse(virDomainDefPtr def)
}
+int
+virDomainIOThreadDefPostParse(virDomainIOThreadIDDefPtr iothread)
+{
+ if ((iothread->poll_grow > 0 || iothread->poll_shrink > 0) &&
+ iothread->poll_max_ns == 0) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("polling grow or shrink is set for iothread id "
+ "'%u' but max_ns is not set"),
+ iothread->iothread_id);
+ return -1;
+ }
+
+ switch (iothread->poll_enabled) {
+ case VIR_TRISTATE_BOOL_ABSENT:
+ if (iothread->poll_max_ns > 0)
+ iothread->poll_enabled = VIR_TRISTATE_BOOL_YES;
+ break;
+
+ case VIR_TRISTATE_BOOL_NO:
+ iothread->poll_max_ns = 0;
+ iothread->poll_grow = 0;
+ iothread->poll_shrink = 0;
+ break;
+
+ case VIR_TRISTATE_BOOL_YES:
+ if (iothread->poll_max_ns == 0) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("polling is enabled for iothread id '%u' but "
+ "max_ns is not set"), iothread->iothread_id);
+ return -1;
+ }
+ break;
+
+ case VIR_TRISTATE_BOOL_LAST:
+ break;
+ }
+
+ return 0;
+}
+
+
+static int
+virDomainDefPostParseIOThreads(virDomainDefPtr def)
+{
+ size_t i;
+
+ for (i = 0; i < def->niothreadids; i++)
+ if (virDomainIOThreadDefPostParse(def->iothreadids[i]) < 0)
+ return -1;
+
+ return 0;
+}
+
+
static int
virDomainDefPostParseInternal(virDomainDefPtr def,
struct virDomainDefPostParseDeviceIteratorData *data)
@@ -4599,6 +4681,9 @@ virDomainDefPostParseInternal(virDomainDefPtr def,
if (virDomainVcpuDefPostParse(def) < 0)
return -1;
+ if (virDomainDefPostParseIOThreads(def) < 0)
+ return -1;
+
if (virDomainDefPostParseMemory(def, data->parseFlags) < 0)
return -1;
@@ -15574,7 +15659,9 @@ virDomainIdmapDefParseXML(xmlXPathContextPtr ctxt,
*
* <iothreads>4</iothreads>
* <iothreadids>
- * <iothread id='1'/>
+ * <iothread id='1'>
+ * <polling enabled='yes' max_ns='4000' grow='2' shrink='4'/>
+ * </iothread>
* <iothread id='3'/>
* <iothread id='5'/>
* <iothread id='7'/>
@@ -15587,6 +15674,7 @@ virDomainIOThreadIDDefParseXML(xmlNodePtr node,
virDomainIOThreadIDDefPtr iothrid;
xmlNodePtr oldnode = ctxt->node;
char *tmp = NULL;
+ int npoll = 0;
if (VIR_ALLOC(iothrid) < 0)
return NULL;
@@ -15604,6 +15692,58 @@ virDomainIOThreadIDDefParseXML(xmlNodePtr node,
_("invalid iothread 'id' value '%s'"), tmp);
goto error;
}
+ VIR_FREE(tmp);
+
+ if ((npoll = virXPathNodeSet("./polling", ctxt, NULL)) < 0)
+ goto error;
+
+ if (npoll > 1) {
+ virReportError(VIR_ERR_XML_ERROR, "%s",
+ _("only one polling element is allowed for each "
+ "<iothread> element"));
+ goto error;
+ }
+
+ if (npoll > 0) {
+ if ((tmp = virXPathString("string(./polling/@enabled)", ctxt))) {
+ int enabled = virTristateBoolTypeFromString(tmp);
+ if (enabled < 0) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("invalid polling 'enabled' value '%s'"), tmp);
+ goto error;
+ }
+ iothrid->poll_enabled = enabled;
+ } else {
+ virReportError(VIR_ERR_XML_ERROR, "%s",
+ _("missing 'enabled' attribute in <polling> element"));
+ goto error;
+ }
+ VIR_FREE(tmp);
+
+ if ((tmp = virXPathString("string(./polling/@max_ns)", ctxt)) &&
+ virStrToLong_uip(tmp, NULL, 10, &iothrid->poll_max_ns) < 0) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("invalid polling 'max_ns' value '%s'"), tmp);
+ goto error;
+ }
+ VIR_FREE(tmp);
+
+ if ((tmp = virXPathString("string(./polling/@grow)", ctxt)) &&
+ virStrToLong_uip(tmp, NULL, 10, &iothrid->poll_grow) < 0) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("invalid polling 'grow' value '%s'"), tmp);
+ goto error;
+ }
+ VIR_FREE(tmp);
+
+ if ((tmp = virXPathString("string(./polling/@shrink)", ctxt)) &&
+ virStrToLong_uip(tmp, NULL, 10, &iothrid->poll_shrink) < 0) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("invalid polling 'shrink' value '%s'"), tmp);
+ goto error;
+ }
+ VIR_FREE(tmp);
+ }
cleanup:
VIR_FREE(tmp);
@@ -23713,7 +23853,8 @@ virDomainDefIothreadShouldFormat(virDomainDefPtr def)
size_t i;
for (i = 0; i < def->niothreadids; i++) {
- if (!def->iothreadids[i]->autofill)
+ if (!def->iothreadids[i]->autofill ||
+ def->iothreadids[i]->poll_enabled != VIR_TRISTATE_BOOL_ABSENT)
return true;
}
@@ -23918,8 +24059,28 @@ virDomainDefFormatInternal(virDomainDefPtr def,
virBufferAddLit(buf, "<iothreadids>\n");
virBufferAdjustIndent(buf, 2);
for (i = 0; i < def->niothreadids; i++) {
- virBufferAsprintf(buf, "<iothread id='%u'/>\n",
- def->iothreadids[i]->iothread_id);
+ virDomainIOThreadIDDefPtr iothread = def->iothreadids[i];
+ virBufferAsprintf(buf, "<iothread id='%u'", iothread->iothread_id);
+ if (iothread->poll_enabled != VIR_TRISTATE_BOOL_ABSENT) {
+ virBufferAddLit(buf, ">\n");
+ virBufferAdjustIndent(buf, 2);
+ virBufferAsprintf(buf, "<polling enabled='%s'",
+ virTristateBoolTypeToString(iothread->poll_enabled));
+ if (iothread->poll_max_ns)
+ virBufferAsprintf(buf, " max_ns='%u'",
+ iothread->poll_max_ns);
+ if (iothread->poll_grow)
+ virBufferAsprintf(buf, " grow='%u'",
+ iothread->poll_grow);
+ if (iothread->poll_shrink)
+ virBufferAsprintf(buf, " shrink='%u'",
+ iothread->poll_shrink);
+ virBufferAddLit(buf, "/>\n");
+ virBufferAdjustIndent(buf, -2);
+ virBufferAddLit(buf, "</iothread>\n");
+ } else {
+ virBufferAddLit(buf, "/>\n");
+ }
}
virBufferAdjustIndent(buf, -2);
virBufferAddLit(buf, "</iothreadids>\n");
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 1e53cc3280..8ac1d8a409 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2074,11 +2074,18 @@ struct _virDomainIOThreadIDDef {
int thread_id;
virBitmapPtr cpumask;
+ virTristateBool poll_enabled;
+ unsigned int poll_max_ns;
+ unsigned int poll_grow;
+ unsigned int poll_shrink;
+
virDomainThreadSchedParam sched;
};
void virDomainIOThreadIDDefFree(virDomainIOThreadIDDefPtr def);
+int virDomainIOThreadDefPostParse(virDomainIOThreadIDDefPtr iothread);
+
typedef struct _virDomainCputune virDomainCputune;
typedef virDomainCputune *virDomainCputunePtr;
@@ -2410,6 +2417,7 @@ typedef enum {
VIR_DOMAIN_DEF_FEATURE_OFFLINE_VCPUPIN = (1 << 2),
VIR_DOMAIN_DEF_FEATURE_NAME_SLASH = (1 << 3),
VIR_DOMAIN_DEF_FEATURE_INDIVIDUAL_VCPUS = (1 << 4),
+ VIR_DOMAIN_DEF_FEATURE_IOTHREAD_POLLING = (1 << 5),
} virDomainDefFeatures;
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index e6ccd697d2..97aee9c0e3 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -371,6 +371,7 @@ virDomainHypervTypeToString;
virDomainInputDefFree;
virDomainIOMMUModelTypeFromString;
virDomainIOMMUModelTypeToString;
+virDomainIOThreadDefPostParse;
virDomainIOThreadIDAdd;
virDomainIOThreadIDDefFree;
virDomainIOThreadIDDel;
diff --git a/tests/genericxml2xmlindata/generic-iothreads-no-polling.xml b/tests/genericxml2xmlindata/generic-iothreads-no-polling.xml
new file mode 100644
index 0000000000..b7e5a11c06
--- /dev/null
+++ b/tests/genericxml2xmlindata/generic-iothreads-no-polling.xml
@@ -0,0 +1,22 @@
+<domain type='qemu'>
+ <name>foo</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <iothreads>2</iothreads>
+ <iothreadids>
+ <iothread id='1'/>
+ <iothread id='2'/>
+ </iothreadids>
+ <os>
+ <type arch='x86_64' machine='pc'>hvm</type>
+ <boot dev='hd'/>
+ </os>
+ <clock offset='utc'/>
+ <on_poweroff>destroy</on_poweroff>
+ <on_reboot>restart</on_reboot>
+ <on_crash>destroy</on_crash>
+ <devices>
+ </devices>
+</domain>
diff --git a/tests/genericxml2xmlindata/generic-iothreads-polling-disabled.xml b/tests/genericxml2xmlindata/generic-iothreads-polling-disabled.xml
new file mode 100644
index 0000000000..0352a80900
--- /dev/null
+++ b/tests/genericxml2xmlindata/generic-iothreads-polling-disabled.xml
@@ -0,0 +1,24 @@
+<domain type='qemu'>
+ <name>foo</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <iothreads>2</iothreads>
+ <iothreadids>
+ <iothread id='1'>
+ <polling enabled='no'/>
+ </iothread>
+ <iothread id='2'/>
+ </iothreadids>
+ <os>
+ <type arch='x86_64' machine='pc'>hvm</type>
+ <boot dev='hd'/>
+ </os>
+ <clock offset='utc'/>
+ <on_poweroff>destroy</on_poweroff>
+ <on_reboot>restart</on_reboot>
+ <on_crash>destroy</on_crash>
+ <devices>
+ </devices>
+</domain>
diff --git a/tests/genericxml2xmlindata/generic-iothreads-polling-enabled-fail.xml b/tests/genericxml2xmlindata/generic-iothreads-polling-enabled-fail.xml
new file mode 100644
index 0000000000..6f77922e7a
--- /dev/null
+++ b/tests/genericxml2xmlindata/generic-iothreads-polling-enabled-fail.xml
@@ -0,0 +1,24 @@
+<domain type='qemu'>
+ <name>foo</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <iothreads>2</iothreads>
+ <iothreadids>
+ <iothread id='1'>
+ <polling enabled='yes'/>
+ </iothread>
+ <iothread id='2'/>
+ </iothreadids>
+ <os>
+ <type arch='x86_64' machine='pc'>hvm</type>
+ <boot dev='hd'/>
+ </os>
+ <clock offset='utc'/>
+ <on_poweroff>destroy</on_poweroff>
+ <on_reboot>restart</on_reboot>
+ <on_crash>destroy</on_crash>
+ <devices>
+ </devices>
+</domain>
diff --git a/tests/genericxml2xmlindata/generic-iothreads-polling-enabled.xml b/tests/genericxml2xmlindata/generic-iothreads-polling-enabled.xml
new file mode 100644
index 0000000000..ef9161f367
--- /dev/null
+++ b/tests/genericxml2xmlindata/generic-iothreads-polling-enabled.xml
@@ -0,0 +1,24 @@
+<domain type='qemu'>
+ <name>foo</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <iothreads>2</iothreads>
+ <iothreadids>
+ <iothread id='1'>
+ <polling enabled='yes' max_ns='4000' grow='50'/>
+ </iothread>
+ <iothread id='2'/>
+ </iothreadids>
+ <os>
+ <type arch='x86_64' machine='pc'>hvm</type>
+ <boot dev='hd'/>
+ </os>
+ <clock offset='utc'/>
+ <on_poweroff>destroy</on_poweroff>
+ <on_reboot>restart</on_reboot>
+ <on_crash>destroy</on_crash>
+ <devices>
+ </devices>
+</domain>
diff --git a/tests/genericxml2xmltest.c b/tests/genericxml2xmltest.c
index 488190270f..c3a9586eab 100644
--- a/tests/genericxml2xmltest.c
+++ b/tests/genericxml2xmltest.c
@@ -100,6 +100,12 @@ mymain(void)
DO_TEST("vcpus-individual");
+ DO_TEST("iothreads-no-polling");
+ DO_TEST("iothreads-polling-enabled");
+ DO_TEST("iothreads-polling-disabled");
+ DO_TEST_FULL("iothreads-polling-enabled-fail", 0, false,
+ TEST_COMPARE_DOM_XML2XML_RESULT_FAIL_PARSE);
+
virObjectUnref(caps);
virObjectUnref(xmlopt);
diff --git a/tests/testutils.c b/tests/testutils.c
index a596a83a96..93a12bcc76 100644
--- a/tests/testutils.c
+++ b/tests/testutils.c
@@ -1101,7 +1101,8 @@ virCapsPtr virTestGenericCapsInit(void)
}
static virDomainDefParserConfig virTestGenericDomainDefParserConfig = {
- .features = VIR_DOMAIN_DEF_FEATURE_INDIVIDUAL_VCPUS,
+ .features = VIR_DOMAIN_DEF_FEATURE_INDIVIDUAL_VCPUS |
+ VIR_DOMAIN_DEF_FEATURE_IOTHREAD_POLLING,
};
static virDomainXMLPrivateDataCallbacks virTestGenericPrivateDataCallbacks;
--
2.11.1
--
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