Random write IOPS will drop dramatically if qcow2 l2 cache could not
cover the whole disk. This patch gives libvirt user a chance to adjust
the qcow2 cache configuration.
Three new qcow2 driver parameters (l2-cache-size, refcount-cache-size
and cache-clean-interval) are added as attributes to a new <qcow2>
subelement for a <driver name='qemu' type='qcow2'...> of a <disk>
element. The QEMU source docs/qcow2-cache.txt provides the guidelines
for defining/configuring values for each.
Signed-off-by: Liu Qing <liuqing@xxxxxxxxxx>
---
change since v4: removed unnecessary cache error check
docs/formatdomain.html.in | 41 +++++++++
docs/schemas/domaincommon.rng | 35 ++++++++
src/conf/domain_conf.c | 97 ++++++++++++++++++++--
src/qemu/qemu_driver.c | 5 ++
src/util/virstoragefile.c | 3 +
src/util/virstoragefile.h | 6 ++
.../qemuxml2argv-disk-drive-qcow2-cache.xml | 43 ++++++++++
.../qemuxml2xmlout-disk-drive-qcow2-cache.xml | 43 ++++++++++
tests/qemuxml2xmltest.c | 1 +
9 files changed, 267 insertions(+), 7 deletions(-)
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.xml
create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-qcow2-cache.xml
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 8ca7637..4574e3a 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -3036,6 +3036,47 @@
set. (<span class="since">Since 3.5.0</span>)
</li>
</ul>
+ The <code>driver</code> element may contain a <code>qcow2</code> sub
+ element, which to specifying further details related to a qcow2 disk.
+ For recommended setting guidelines refer to the QEMU source file
+ <code>docs/qcow2-cache.txt</code>.
+ <span class="since">Since 3.8.0</span>
+ <ul>
+ <li>
+ The optional <code>l2_cache_size</code> attribute controls how much
+ memory will be consumed by qcow2 l2 table cache in bytes. This
+ option is only valid when the driver type is qcow2. The default
+ size is 2097152.
+ <span class='since'>Since 3.8.0</span>
+
+ <b>In general you should leave this option alone, unless you
+ are very certain you know what you are doing.</b>
+ </li>
+ <li>
+ The optional <code>refcount_cache_size</code> attribute controls
+ how much memory will be consumed by qcow2 reference count table
+ cache in bytes. This option is only valid when the driver type is
+ qcow2. The default size is 262144.
+ <span class='since'>Since 3.8.0</span>
+
+ <b>In general you should leave this option alone, unless you
+ are very certain you know what you are doing.</b>
+ </li>
+ <li>
+ The optional <code>cache_clean_interval</code> attribute defines
+ an interval (in seconds). All cache entries that haven't been
+ accessed during that interval are removed from memory. This option
+ is only valid when the driver type is qcow2. The default
+ value is 0, which disables this feature. If the interval is too
+ short, it will cause frequent cache write back and load, which
+ impact performance. If the interval is too long, unused cache
+ will still consume memory until it's been written back to disk.
+ <span class='since'>Since 3.8.0</span>
+
+ <b>In general you should leave this option alone, unless you
+ are very certain you know what you are doing.</b>
+ </li>
+ </ul>
</dd>
<dt><code>backenddomain</code></dt>
<dd>The optional <code>backenddomain</code> element allows specifying a
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index c9a4f7a..0e25f44 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -1756,6 +1756,23 @@
</element>
</define>
<!--
+ Parameters for qcow2 driver
+ -->
+ <define name="qcow2Driver">
+ <element name="qcow2">
+ <optional>
+ <ref name="qcow2_l2_cache_size"/>
+ </optional>
+ <optional>
+ <ref name="qcow2_refcount_cache_size"/>
+ </optional>
+ <optional>
+ <ref name="qcow2_cache_clean_interval"/>
+ </optional>
+ </element>
+ </define>
+
+ <!--
Disk may use a special driver for access.
-->
<define name="diskDriver">
@@ -1794,6 +1811,9 @@
<ref name="detect_zeroes"/>
</optional>
<ref name="virtioOptions"/>
+ <optional>
+ <ref name="qcow2Driver"/>
+ </optional>
<empty/>
</element>
</define>
@@ -1889,6 +1909,21 @@
</choice>
</attribute>
</define>
+ <define name="qcow2_l2_cache_size">
+ <attribute name='l2_cache_size'>
+ <ref name="unsignedLong"/>
+ </attribute>
+ </define>
+ <define name="qcow2_refcount_cache_size">
+ <attribute name='refcount_cache_size'>
+ <ref name="unsignedLong"/>
+ </attribute>
+ </define>
+ <define name="qcow2_cache_clean_interval">
+ <attribute name='cache_clean_interval'>
+ <ref name="unsignedLong"/>
+ </attribute>
+ </define>
<define name="controller">
<element name="controller">
<optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index a43b25c..f225a7f 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -5734,6 +5734,30 @@ virDomainDeviceLoadparmIsValid(const char *loadparm)
static void
+virDomainQcow2CacheOptionsFormat(virBufferPtr buf,
+ virDomainDiskDefPtr def)
+{
+ if (def->src->l2_cache_size == 0 &&
+ def->src->refcount_cache_size == 0 &&
+ def->src->cache_clean_interval == 0)
+ return;
+
+ virBufferAddLit(buf, "<qcow2");
+
+ if (def->src->l2_cache_size > 0)
+ virBufferAsprintf(buf, " l2_cache_size='%llu'",
+ def->src->l2_cache_size);
+ if (def->src->refcount_cache_size > 0)
+ virBufferAsprintf(buf, " refcount_cache_size='%llu'",
+ def->src->refcount_cache_size);
+ if (def->src->cache_clean_interval > 0)
+ virBufferAsprintf(buf, " cache_clean_interval='%llu'",
+ def->src->cache_clean_interval);
+ virBufferAddLit(buf, "/>\n");
+}
+
+
+static void
virDomainVirtioOptionsFormat(virBufferPtr buf,
virDomainVirtioOptionsPtr virtio)
{
@@ -8572,15 +8596,69 @@ virDomainDiskDefParseValidate(const virDomainDiskDef *def)
}
}
+ if (def->src->format != VIR_STORAGE_FILE_QCOW2 &&
+ (def->src->l2_cache_size > 0 || def->src->refcount_cache_size > 0 ||
+ def->src->cache_clean_interval > 0)) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("Setting l2_cache_size, refcount_cache_size, "
+ "cache_clean_interval is not allowed for types "
+ "other than QCOW2"));
+ return -1;
+ }
+
return 0;
}
static int
+virDomainDiskDefQcow2ParseXML(virDomainDiskDefPtr def,
+ xmlNodePtr cur)
+{
+ char *tmp = NULL;
+ int ret = -1;
+
+ if ((tmp = virXMLPropString(cur, "l2_cache_size")) &&
+ (virStrToLong_ullp(tmp, NULL, 10, &def->src->l2_cache_size) < 0)) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("Invalid l2_cache_size attribute in disk "
+ "driver element: %s"), tmp);
+ goto cleanup;
+ }
+ VIR_FREE(tmp);
+
+ if ((tmp = virXMLPropString(cur, "refcount_cache_size")) &&
+ (virStrToLong_ullp(tmp, NULL, 10, &def->src->refcount_cache_size) < 0)) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("Invalid refcount_cache_size attribute in disk "
+ "driver element: %s"), tmp);
+ goto cleanup;
+ }
+ VIR_FREE(tmp);
+
+ if ((tmp = virXMLPropString(cur, "cache_clean_interval")) &&
+ (virStrToLong_ullp(tmp, NULL, 10, &def->src->cache_clean_interval) < 0)) {
+ virReportError(VIR_ERR_XML_ERROR,
+ _("Invalid cache_clean_interval attribute in "
+ "disk driver element: %s"), tmp);
+ goto cleanup;
+ }
+ VIR_FREE(tmp);
+
+ ret = 0;
+
+ cleanup:
+ VIR_FREE(tmp);
+
+ return ret;
+}
+
+
+static int
virDomainDiskDefDriverParseXML(virDomainDiskDefPtr def,
xmlNodePtr cur)
{
char *tmp = NULL;
+ xmlNodePtr child;
int ret = -1;
def->src->driverName = virXMLPropString(cur, "name");
@@ -8683,6 +8761,13 @@ virDomainDiskDefDriverParseXML(virDomainDiskDefPtr def,
}
VIR_FREE(tmp);
+ for (child = cur->children; child != NULL; child = child->next) {
+ if (virXMLNodeNameEqual(child, "qcow2") &&
+ virDomainDiskDefQcow2ParseXML(def, child) < 0) {
+ goto cleanup;
+ }
+ }
+
ret = 0;
cleanup:
@@ -21885,6 +21970,7 @@ virDomainDiskDefFormat(virBufferPtr buf,
const char *discard = virDomainDiskDiscardTypeToString(def->discard);
const char *detect_zeroes = virDomainDiskDetectZeroesTypeToString(def->detect_zeroes);
virBuffer driverBuf = VIR_BUFFER_INITIALIZER;
+ virBuffer driverQcow2Buf = VIR_BUFFER_INITIALIZER;
if (!type || !def->src->type) {
virReportError(VIR_ERR_INTERNAL_ERROR,
@@ -21963,14 +22049,11 @@ virDomainDiskDefFormat(virBufferPtr buf,
virDomainVirtioOptionsFormat(&driverBuf, def->virtio);
- if (virBufferCheckError(&driverBuf) < 0)
- return -1;
+ virBufferSetChildIndent(&driverQcow2Buf, buf);
+ virDomainQcow2CacheOptionsFormat(&driverQcow2Buf, def);
- if (virBufferUse(&driverBuf)) {
- virBufferAddLit(buf, "<driver");
- virBufferAddBuffer(buf, &driverBuf);
- virBufferAddLit(buf, "/>\n");
- }
+ if (virXMLFormatElement(buf, "driver", &driverBuf, &driverQcow2Buf) < 0)
+ return -1;
if (def->src->auth) {
if (virStorageAuthDefFormat(buf, def->src->auth) < 0)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index e956839..c3b81e1 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -14318,6 +14318,11 @@ qemuDomainSnapshotDiskDataCollect(virQEMUDriverPtr driver,
if (!(dd->src = virStorageSourceCopy(snap->def->disks[i].src, false)))
goto error;
+ /* keep the qcow2 cache configuration */
+ dd->src->l2_cache_size = vm->def->disks[i]->src->l2_cache_size;
+ dd->src->refcount_cache_size = vm->def->disks[i]->src->refcount_cache_size;
+ dd->src->cache_clean_interval = vm->def->disks[i]->src->cache_clean_interval;
+
if (virStorageSourceInitChainElement(dd->src, dd->disk->src, false) < 0)
goto error;
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index e94ad32..f23390f 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -2038,6 +2038,9 @@ virStorageSourceCopy(const virStorageSource *src,
ret->physical = src->physical;
ret->readonly = src->readonly;
ret->shared = src->shared;
+ ret->l2_cache_size = src->l2_cache_size;
+ ret->refcount_cache_size = src->refcount_cache_size;
+ ret->cache_clean_interval = src->cache_clean_interval;
/* storage driver metadata are not copied */
ret->drv = NULL;
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index 6c388b1..9b5a5f3 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -280,6 +280,12 @@ struct _virStorageSource {
/* metadata that allows identifying given storage source */
char *nodeformat; /* name of the format handler object */
char *nodestorage; /* name of the storage object */
+
+ unsigned long long l2_cache_size; /* qcow2 l2 cache size */
+ /* qcow2 reference count table cache size */
+ unsigned long long refcount_cache_size;
+ /* clean unused cache entries interval */
+ unsigned long long cache_clean_interval;
};
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.xml b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.xml
new file mode 100644
index 0000000..3f464db
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-qcow2-cache.xml
@@ -0,0 +1,43 @@
+<domain type='qemu'>
+ <name>QEMUGuest1</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <os>
+ <type arch='i686' 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>
+ <emulator>/usr/bin/qemu-system-i686</emulator>
+ <disk type='block' device='disk'>
+ <driver name='qemu' type='qcow2' cache='none'>
+ <qcow2 l2_cache_size='2097152' refcount_cache_size='524288' cache_clean_interval='900'/>
+ </driver>
+ <source dev='/dev/HostVG/QEMUGuest1'/>
+ <target dev='hda' bus='ide'/>
+ <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+ </disk>
+ <disk type='block' device='cdrom'>
+ <driver name='qemu' type='raw'/>
+ <source dev='/dev/HostVG/QEMUGuest2'/>
+ <target dev='hdc' bus='ide'/>
+ <readonly/>
+ <address type='drive' controller='0' bus='1' target='0' unit='0'/>
+ </disk>
+ <controller type='usb' index='0'>
+ <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+ </controller>
+ <controller type='ide' index='0'>
+ <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+ </controller>
+ <controller type='pci' index='0' model='pci-root'/>
+ <input type='mouse' bus='ps2'/>
+ <input type='keyboard' bus='ps2'/>
+ <memballoon model='none'/>
+ </devices>
+</domain>
diff --git a/tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-qcow2-cache.xml b/tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-qcow2-cache.xml
new file mode 100644
index 0000000..3f464db
--- /dev/null
+++ b/tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-drive-qcow2-cache.xml
@@ -0,0 +1,43 @@
+<domain type='qemu'>
+ <name>QEMUGuest1</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219136</memory>
+ <currentMemory unit='KiB'>219136</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <os>
+ <type arch='i686' 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>
+ <emulator>/usr/bin/qemu-system-i686</emulator>
+ <disk type='block' device='disk'>
+ <driver name='qemu' type='qcow2' cache='none'>
+ <qcow2 l2_cache_size='2097152' refcount_cache_size='524288' cache_clean_interval='900'/>
+ </driver>
+ <source dev='/dev/HostVG/QEMUGuest1'/>
+ <target dev='hda' bus='ide'/>
+ <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+ </disk>
+ <disk type='block' device='cdrom'>
+ <driver name='qemu' type='raw'/>
+ <source dev='/dev/HostVG/QEMUGuest2'/>
+ <target dev='hdc' bus='ide'/>
+ <readonly/>
+ <address type='drive' controller='0' bus='1' target='0' unit='0'/>
+ </disk>
+ <controller type='usb' index='0'>
+ <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+ </controller>
+ <controller type='ide' index='0'>
+ <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+ </controller>
+ <controller type='pci' index='0' model='pci-root'/>
+ <input type='mouse' bus='ps2'/>
+ <input type='keyboard' bus='ps2'/>
+ <memballoon model='none'/>
+ </devices>
+</domain>
diff --git a/tests/qemuxml2xmltest.c b/tests/qemuxml2xmltest.c
index 0a87ced..fab1e19 100644
--- a/tests/qemuxml2xmltest.c
+++ b/tests/qemuxml2xmltest.c
@@ -461,6 +461,7 @@ mymain(void)
DO_TEST("disk-drive-cache-v2-none", NONE);
DO_TEST("disk-drive-cache-directsync", NONE);
DO_TEST("disk-drive-cache-unsafe", NONE);
+ DO_TEST("disk-drive-qcow2-cache", NONE);
DO_TEST("disk-drive-network-nbd", NONE);
DO_TEST("disk-drive-network-nbd-export", NONE);
DO_TEST("disk-drive-network-nbd-ipv6", NONE);
--
1.8.3.1
--
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