[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

[libvirt] [PATCHv2] netcf driver: use a single netcf handle for all connections



This resolves: https://bugzilla.redhat.com/show_bug.cgi?id=983026

The netcf interface driver previously had no state driver associated
with it - as a connection was opened, it would create a new netcf
instance just for that connection, and close it when it was
finished. the problem with this is that each connection to libvirt
used up a netlink socket, and there is a per process maximum of ~1000
netlink sockets.

The solution is to create a state driver to go along with the netcf
driver. The state driver will opens a netcf instance, then all
connections share that same netcf instance, thus only a single
netlink socket will be used no matter how many connections are mde to
libvirtd.

This was rather simple to do - a new virObjectLockable class is
created for the single driverState object, which is created in
netcfStateInitialize and contains the single netcf handle; instead of
creating a new object for each client connection, netcfInterfaceOpen
now just increments the driverState object's reference count and puts
a pointer to it into the connection's privateData. Similarly,
netcfInterfaceClose() just un-refs the driverState object (as does
netcfStateCleanup()), and virNetcfInterfaceDriverStateDispose()
handles closing the netcf instance. Since all the functions already
have locking around them, the static lock functions used by all
functions just needed to be changed to call virObjectLock() and
virObjectUnlock() instead of directly calling the virMutex* functions.
---
Changes from V1:

* make driverState a static.

* switch to using a virObjectLockable for driverState, at
  Eric's suggestion.

* add a simple error message if ncf_init() fails.

Again, I've tried this with a small number of simultaneous connections
(including virt-manager), but I don't have a ready-made stress test.


 src/interface/interface_backend_netcf.c | 173 +++++++++++++++++++++++---------
 1 file changed, 125 insertions(+), 48 deletions(-)

diff --git a/src/interface/interface_backend_netcf.c b/src/interface/interface_backend_netcf.c
index f47669e..627c225 100644
--- a/src/interface/interface_backend_netcf.c
+++ b/src/interface/interface_backend_netcf.c
@@ -41,19 +41,119 @@
 /* Main driver state */
 typedef struct
 {
-    virMutex lock;
+    virObjectLockable parent;
     struct netcf *netcf;
 } virNetcfDriverState, *virNetcfDriverStatePtr;
 
+static virClassPtr virNetcfDriverStateClass;
+static void virNetcfDriverStateDispose(void *obj);
 
-static void interfaceDriverLock(virNetcfDriverStatePtr driver)
+static int
+virNetcfDriverStateOnceInit(void)
+{
+    if (!(virNetcfDriverStateClass = virClassNew(virClassForObjectLockable(),
+                                       "virNetcfDriverState",
+                                       sizeof(virNetcfDriverState),
+                                       virNetcfDriverStateDispose)))
+        return -1;
+    return 0;
+}
+
+VIR_ONCE_GLOBAL_INIT(virNetcfDriverState)
+
+static virNetcfDriverStatePtr driverState = NULL;
+
+static void
+virNetcfDriverStateDispose(void *obj)
+{
+    virNetcfDriverStatePtr driver = obj;
+
+    if (driver->netcf)
+        ncf_close(driver->netcf);
+}
+
+static void
+interfaceDriverLock(virNetcfDriverStatePtr driver)
+{
+    virObjectLock(driver);
+}
+
+static void
+interfaceDriverUnlock(virNetcfDriverStatePtr driver)
+{
+    virObjectUnlock(driver);
+}
+
+static int
+netcfStateInitialize(bool privileged ATTRIBUTE_UNUSED,
+                     virStateInhibitCallback callback ATTRIBUTE_UNUSED,
+                     void *opaque ATTRIBUTE_UNUSED)
+{
+    if (virNetcfDriverStateInitialize() < 0)
+        return -1;
+
+    if (!(driverState = virObjectLockableNew(virNetcfDriverStateClass)))
+        return -1;
+
+    /* open netcf */
+    if (ncf_init(&driverState->netcf, NULL) != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("failed to initialize netcf"));
+        virObjectUnref(driverState);
+        driverState = NULL;
+        return -1;
+    }
+    return 0;
+}
+
+static int
+netcfStateCleanup(void)
 {
-    virMutexLock(&driver->lock);
+    if (!driverState) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Attempt to close netcf state driver already closed"));
+        return -1;
+    }
+
+    if (virObjectUnref(driverState)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Attempt to close netcf state driver "
+                         "with open connections"));
+        return -1;
+    }
+    driverState = NULL;
+    return 0;
 }
 
-static void interfaceDriverUnlock(virNetcfDriverStatePtr driver)
+static int
+netcfStateReload(void)
 {
-    virMutexUnlock(&driver->lock);
+    int ret = -1;
+
+    if (!driverState)
+        return 0;
+
+    interfaceDriverLock(driverState);
+    ncf_close(driverState->netcf);
+    if (ncf_init(&driverState->netcf, NULL) != 0)
+    {
+        /* this isn't a good situation, because we can't shut down the
+         * driver as there may still be connections to it. If we set
+         * the netcf handle to NULL, any subsequent calls to netcf
+         * will just fail rather than causing a crash. Not ideal, but
+         * livable (since this should never happen).
+         */
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("failed to re-init netcf"));
+        driverState->netcf = NULL;
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    interfaceDriverUnlock(driverState);
+
+    return ret;
 }
 
 /*
@@ -148,61 +248,30 @@ static struct netcf_if *interfaceDriverGetNetcfIF(struct netcf *ncf, virInterfac
     return iface;
 }
 
-static virDrvOpenStatus netcfInterfaceOpen(virConnectPtr conn,
-                                           virConnectAuthPtr auth ATTRIBUTE_UNUSED,
-                                           unsigned int flags)
+static virDrvOpenStatus
+netcfInterfaceOpen(virConnectPtr conn,
+                   virConnectAuthPtr auth ATTRIBUTE_UNUSED,
+                   unsigned int flags)
 {
-    virNetcfDriverStatePtr driverState;
-
     virCheckFlags(VIR_CONNECT_RO, VIR_DRV_OPEN_ERROR);
 
-    if (VIR_ALLOC(driverState) < 0)
-        goto alloc_error;
-
-    /* initialize non-0 stuff in driverState */
-    if (virMutexInit(&driverState->lock) < 0)
-    {
-        /* what error to report? */
-        goto mutex_error;
-    }
-
-    /* open netcf */
-    if (ncf_init(&driverState->netcf, NULL) != 0)
-    {
-        /* what error to report? */
-        goto netcf_error;
-    }
+    if (!driverState)
+        return VIR_DRV_OPEN_ERROR;
 
+    virObjectRef(driverState);
     conn->interfacePrivateData = driverState;
     return VIR_DRV_OPEN_SUCCESS;
-
-netcf_error:
-    if (driverState->netcf)
-    {
-        ncf_close(driverState->netcf);
-    }
-    virMutexDestroy(&driverState->lock);
-mutex_error:
-    VIR_FREE(driverState);
-alloc_error:
-    return VIR_DRV_OPEN_ERROR;
 }
 
-static int netcfInterfaceClose(virConnectPtr conn)
+static int
+netcfInterfaceClose(virConnectPtr conn)
 {
 
     if (conn->interfacePrivateData != NULL)
     {
-        virNetcfDriverStatePtr driver = conn->interfacePrivateData;
-
-        /* close netcf instance */
-        ncf_close(driver->netcf);
-        /* destroy lock */
-        virMutexDestroy(&driver->lock);
-        /* free driver state */
-        VIR_FREE(driver);
+        virObjectUnref(conn->interfacePrivateData);
+        conn->interfacePrivateData = NULL;
     }
-    conn->interfacePrivateData = NULL;
     return 0;
 }
 
@@ -1070,7 +1139,7 @@ static int netcfInterfaceChangeRollback(virConnectPtr conn, unsigned int flags)
 #endif /* HAVE_NETCF_TRANSACTIONS */
 
 static virInterfaceDriver interfaceDriver = {
-    "netcf",
+    .name = INTERFACE_DRIVER_NAME,
     .interfaceOpen = netcfInterfaceOpen, /* 0.7.0 */
     .interfaceClose = netcfInterfaceClose, /* 0.7.0 */
     .connectNumOfInterfaces = netcfConnectNumOfInterfaces, /* 0.7.0 */
@@ -1093,11 +1162,19 @@ static virInterfaceDriver interfaceDriver = {
 #endif /* HAVE_NETCF_TRANSACTIONS */
 };
 
+static virStateDriver interfaceStateDriver = {
+    .name = INTERFACE_DRIVER_NAME,
+    .stateInitialize = netcfStateInitialize,
+    .stateCleanup = netcfStateCleanup,
+    .stateReload = netcfStateReload,
+};
+
 int netcfIfaceRegister(void) {
     if (virRegisterInterfaceDriver(&interfaceDriver) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("failed to register netcf interface driver"));
         return -1;
     }
+    virRegisterStateDriver(&interfaceStateDriver);
     return 0;
 }
-- 
1.7.11.7


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]