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[libvirt] [PATCH v2] Support for qemu aio drive option



Revised patch against libvirt 0.7.6 to support qemu's aio option.

qemu allows the user to choose what io storage api should be used, either the
default (threads) or native (linux aio) which in the latter case can result in
better performance.

This patch exposes this functionality through libvirt.

Thanks a lot to Eric Blake and Matthias Bolte for their comments.
---
 docs/formatdomain.html.in |    4 +++-
 docs/schemas/domain.rng   |   13 +++++++++++--
 src/conf/domain_conf.c    |   23 +++++++++++++++++++++++
 src/conf/domain_conf.h    |   10 ++++++++++
 src/qemu/qemu_conf.c      |   14 ++++++++++++++
 src/qemu/qemu_conf.h      |    2 ++
 6 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index ce49f7d..ec85ef3 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -478,7 +478,9 @@
         attribute is the primary backend driver name, while the optional <code>type</code>
         attribute provides the sub-type. The optional <code>cache</code> attribute
         controls the cache mechanism, possible values are "default", "none",
-        "writethrough" and "writeback". <span class="since">Since 0.1.8</span>
+        "writethrough" and "writeback". Specific to KVM guests is the optional <code>aio</code>
+        attribute which controls what storage api is used for io operations, its possible
+        values are "threads" and "native". <span class="since">Since 0.1.8; "aio" attribute since 0.7.7</span>
       </dd>
       <dt><code>encryption</code></dt>
       <dd>If present, specifies how the volume is encrypted.  See
diff --git a/docs/schemas/domain.rng b/docs/schemas/domain.rng
index bb6d00d..5d2dafe 100644
--- a/docs/schemas/domain.rng
+++ b/docs/schemas/domain.rng
@@ -499,8 +499,9 @@
           <ref name="driverCache"/>
         </group>
       </choice>
-      <empty/>
-    </element>
+      <optional>
+        <ref name="driverAIO"/>
+      </optional>
   </define>
   <define name="driverFormat">
     <attribute name="name">
@@ -521,6 +522,14 @@
       </choice>
     </attribute>
   </define>
+  <define name="driverAIO">
+    <attribute name="aio">
+      <choice>
+        <value>threads</value>
+        <value>native</value>
+      </choice>
+    </attribute>
+  </define>
   <define name="controller">
     <element name="controller">
       <optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 766993c..8bee7b8 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -120,6 +120,11 @@ VIR_ENUM_IMPL(virDomainDiskCache, VIR_DOMAIN_DISK_CACHE_LAST,
               "writethrough",
               "writeback")
 
+VIR_ENUM_IMPL(virDomainDiskAIO, VIR_DOMAIN_DISK_AIO_LAST,
+              "default",
+              "native",
+              "threads")
+
 VIR_ENUM_IMPL(virDomainController, VIR_DOMAIN_CONTROLLER_TYPE_LAST,
               "ide",
               "fdc",
@@ -1228,6 +1233,7 @@ virDomainDiskDefParseXML(virConnectPtr conn,
     char *target = NULL;
     char *bus = NULL;
     char *cachetag = NULL;
+    char *aiotag = NULL;
     char *devaddr = NULL;
     virStorageEncryptionPtr encryption = NULL;
     char *serial = NULL;
@@ -1293,6 +1299,7 @@ virDomainDiskDefParseXML(virConnectPtr conn,
                 driverName = virXMLPropString(cur, "name");
                 driverType = virXMLPropString(cur, "type");
                 cachetag = virXMLPropString(cur, "cache");
+                aiotag = virXMLPropString(cur, "aio");
             } else if (xmlStrEqual(cur->name, BAD_CAST "readonly")) {
                 def->readonly = 1;
             } else if (xmlStrEqual(cur->name, BAD_CAST "shareable")) {
@@ -1409,6 +1416,13 @@ virDomainDiskDefParseXML(virConnectPtr conn,
         goto error;
     }
 
+    if (aiotag &&
+        (def->aiomode = virDomainDiskAIOTypeFromString(aiotag)) < 0) {
+        virDomainReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                             _("unknown disk aio mode '%s'"), aiotag);
+        goto error;
+    }
+
     if (devaddr) {
         if (sscanf(devaddr, "%x:%x:%x",
                    &def->info.addr.pci.domain,
@@ -1450,6 +1464,7 @@ cleanup:
     VIR_FREE(driverType);
     VIR_FREE(driverName);
     VIR_FREE(cachetag);
+    VIR_FREE(aiotag);
     VIR_FREE(devaddr);
     VIR_FREE(serial);
     virStorageEncryptionFree(encryption);
@@ -4565,6 +4580,7 @@ virDomainDiskDefFormat(virConnectPtr conn,
     const char *device = virDomainDiskDeviceTypeToString(def->device);
     const char *bus = virDomainDiskBusTypeToString(def->bus);
     const char *cachemode = virDomainDiskCacheTypeToString(def->cachemode);
+    const char *aiomode = virDomainDiskAIOTypeToString(def->aiomode);
 
     if (!type) {
         virDomainReportError(conn, VIR_ERR_INTERNAL_ERROR,
@@ -4586,6 +4602,11 @@ virDomainDiskDefFormat(virConnectPtr conn,
                              _("unexpected disk cache mode %d"), def->cachemode);
         return -1;
     }
+    if (!aiomode) {
+        virDomainReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                             _("unexpected disk aio mode %d"), def->aiomode);
+        return -1;
+    }
 
     virBufferVSprintf(buf,
                       "    <disk type='%s' device='%s'>\n",
@@ -4597,6 +4618,8 @@ virDomainDiskDefFormat(virConnectPtr conn,
             virBufferVSprintf(buf, " type='%s'", def->driverType);
         if (def->cachemode)
             virBufferVSprintf(buf, " cache='%s'", cachemode);
+        if (def->aiomode)
+            virBufferVSprintf(buf, " aio='%s'", aiomode);
         virBufferVSprintf(buf, "/>\n");
     }
 
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 0b79e88..07805a6 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -141,6 +141,14 @@ enum  virDomainDiskCache {
     VIR_DOMAIN_DISK_CACHE_LAST
 };
 
+enum  virDomainDiskAIO {
+    VIR_DOMAIN_DISK_AIO_DEFAULT,
+    VIR_DOMAIN_DISK_AIO_NATIVE,
+    VIR_DOMAIN_DISK_AIO_THREADS,
+
+    VIR_DOMAIN_DISK_AIO_LAST
+};
+
 /* Stores the virtual disk configuration */
 typedef struct _virDomainDiskDef virDomainDiskDef;
 typedef virDomainDiskDef *virDomainDiskDefPtr;
@@ -154,6 +162,7 @@ struct _virDomainDiskDef {
     char *driverType;
     char *serial;
     int cachemode;
+    int aiomode;
     unsigned int readonly : 1;
     unsigned int shared : 1;
     virDomainDeviceInfo info;
@@ -897,6 +906,7 @@ VIR_ENUM_DECL(virDomainDisk)
 VIR_ENUM_DECL(virDomainDiskDevice)
 VIR_ENUM_DECL(virDomainDiskBus)
 VIR_ENUM_DECL(virDomainDiskCache)
+VIR_ENUM_DECL(virDomainDiskAIO)
 VIR_ENUM_DECL(virDomainController)
 VIR_ENUM_DECL(virDomainFS)
 VIR_ENUM_DECL(virDomainNet)
diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 3d83a8f..fd3a670 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -83,6 +83,12 @@ VIR_ENUM_IMPL(qemuDiskCacheV2, VIR_DOMAIN_DISK_CACHE_LAST,
               "writethrough",
               "writeback");
 
+VIR_ENUM_DECL(qemuDiskAIO)
+VIR_ENUM_IMPL(qemuDiskAIO, VIR_DOMAIN_DISK_AIO_LAST,
+              "default",
+              "native",
+              "threads");
+
 VIR_ENUM_DECL(qemuVideo)
 
 VIR_ENUM_IMPL(qemuVideo, VIR_DOMAIN_VIDEO_TYPE_LAST,
@@ -1137,6 +1143,8 @@ static unsigned int qemudComputeCmdFlags(const char *help,
             flags |= QEMUD_CMD_FLAG_DRIVE_CACHE_V2;
         if (strstr(help, "format="))
             flags |= QEMUD_CMD_FLAG_DRIVE_FORMAT;
+        if (strstr(help, "aio=threads|native"))
+            flags |= QEMUD_CMD_FLAG_DRIVE_AIO;
     }
     if (strstr(help, "-vga") && !strstr(help, "-std-vga"))
         flags |= QEMUD_CMD_FLAG_VGA;
@@ -2340,6 +2348,12 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         virBufferAddLit(&opt, ",cache=off");
     }
 
+    if (disk->aiomode && (qemuCmdFlags & QEMUD_CMD_FLAG_DRIVE_AIO)) {
+        const char * mode = qemuDiskAIOTypeToString(disk->aiomode);
+
+        virBufferVSprintf(&opt, ",aio=%s", mode);
+    }
+
     if (virBufferError(&opt)) {
         virReportOOMError(NULL);
         goto error;
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index 101f187..780ae6e 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -82,6 +82,8 @@ enum qemud_cmd_flags {
     QEMUD_CMD_FLAG_SDL           = (1 << 27), /* Is the new -sdl arg available */
     QEMUD_CMD_FLAG_SMP_TOPOLOGY  = (1 << 28), /* Is sockets=s,cores=c,threads=t available for -smp? */
     QEMUD_CMD_FLAG_NETDEV        = (1 << 29), /* The -netdev flag & netdev_add/remove monitor commands */
+
+    QEMUD_CMD_FLAG_DRIVE_AIO     = (1 << 30), /* Is -drive aio= avail */
 };
 
 /* Main driver state */
-- 
1.7.0.4


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