qemu: Introduce job queue size limit

This patch creates an optional BeginJob queue size limit. When
active, all other attempts above level will fail. To set this
feature assign desired value to max_queued variable in qemu.conf.
Setting it to 0 turns it off.

diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
index d018ac259d01ddbf1bd51aef1b36ff77b4b7f5b1..6c145c7d82cc3396840049aeeab19f8360af58ce 100644 (file)
--- a/src/qemu/libvirtd_qemu.aug
+++ b/src/qemu/libvirtd_qemu.aug
@@ -51,6 +51,7 @@ module Libvirtd_qemu =
                  | bool_entry "set_process_name"
                  | int_entry "max_processes"
                  | str_entry "lock_manager"
+                 | int_entry "max_queued"
 
    (* Each enty in the config is one of the following three ... *)
    let entry = vnc_entry

diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
index 79c6e8510b5dd795af6c47c9eddc0a730c48f8b4..4da5d5a13fddcd0391f15c2050f1657686483d9c 100644 (file)
--- a/src/qemu/qemu.conf
+++ b/src/qemu/qemu.conf
@@ -309,3 +309,10 @@
 # disk), uncomment this
 #
 # lock_manager = "sanlock"
+
+# Set limit of maximum APIs queued on one domain. All other APIs
+# over this threshold will fail on acquiring job lock. Specially,
+# setting to zero turns this feature off.
+# Note, that job lock is per domain.
+#
+# max_queued = 0

diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 443e08d7bbccdf0effc37760fc4b55bfe615b909..d1bf075659f433b6e5144cbd0f0f34ce86db4f2e 100644 (file)
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -458,6 +458,10 @@ int qemudLoadDriverConfig(struct qemud_driver *driver,
         VIR_FREE(lockConf);
     }
 
+    p = virConfGetValue(conf, "max_queued");
+    CHECK_TYPE("max_queued", VIR_CONF_LONG);
+    if (p) driver->max_queued = p->l;
+
     virConfFree (conf);
     return 0;
 }

diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index 5469a63abef9be761bd46810693080c9401b2ec2..e8b92a49820337bc9b8bdf85834ab9b25da3cb71 100644 (file)
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -109,6 +109,8 @@ struct qemud_driver {
 
     int maxProcesses;
 
+    int max_queued;
+
     virCapsPtr caps;
 
     virDomainEventStatePtr domainEventState;

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 675c6dff9b068047387096c409dfd4492acc7275..982bad6c7e8f7ed283df5e6d13e6babfe3e08add 100644 (file)
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -713,6 +713,8 @@ qemuDomainObjBeginJobInternal(struct qemud_driver *driver,
     unsigned long long then;
     bool nested = job == QEMU_JOB_ASYNC_NESTED;
 
+    priv->jobs_queued++;
+
     if (virTimeMs(&now) < 0)
         return -1;
     then = now + QEMU_JOB_WAIT_TIME;
@@ -722,6 +724,11 @@ qemuDomainObjBeginJobInternal(struct qemud_driver *driver,
         qemuDriverUnlock(driver);
 
 retry:
+    if (driver->max_queued &&
+        priv->jobs_queued > driver->max_queued) {
+        goto error;
+    }
+
     while (!nested && !qemuDomainJobAllowed(priv, job)) {
         if (virCondWaitUntil(&priv->job.asyncCond, &obj->lock, then) < 0)
             goto error;
@@ -761,9 +768,15 @@ error:
     if (errno == ETIMEDOUT)
         qemuReportError(VIR_ERR_OPERATION_TIMEOUT,
                         "%s", _("cannot acquire state change lock"));
+    else if (driver->max_queued &&
+             priv->jobs_queued > driver->max_queued)
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        "%s", _("cannot acquire state change lock "
+                                "due to max_queued limit"));
     else
         virReportSystemError(errno,
                              "%s", _("cannot acquire job mutex"));
+    priv->jobs_queued--;
     if (driver_locked) {
         virDomainObjUnlock(obj);
         qemuDriverLock(driver);
@@ -844,6 +857,8 @@ int qemuDomainObjEndJob(struct qemud_driver *driver, virDomainObjPtr obj)
 {
     qemuDomainObjPrivatePtr priv = obj->privateData;
 
+    priv->jobs_queued--;
+
     qemuDomainObjResetJob(priv);
     qemuDomainObjSaveJob(driver, obj);
     virCondSignal(&priv->job.cond);
@@ -856,6 +871,8 @@ qemuDomainObjEndAsyncJob(struct qemud_driver *driver, virDomainObjPtr obj)
 {
     qemuDomainObjPrivatePtr priv = obj->privateData;
 
+    priv->jobs_queued--;
+
     qemuDomainObjResetAsyncJob(priv);
     qemuDomainObjSaveJob(driver, obj);
     virCondBroadcast(&priv->job.asyncCond);

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index e12ca8e8f60ab130f9d39258ae7060b1392271f2..55875fe4dec223200793859a8bc0caf5c73c14bd 100644 (file)
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -113,6 +113,8 @@ struct _qemuDomainObjPrivate {
     char *lockState;
 
     bool fakeReboot;
+
+    int jobs_queued;
 };
 
 struct qemuDomainWatchdogEvent