nodeinfo: Add check and workaround to guarantee valid cpu topologies

Lately there were a few reports of the output of the virsh nodeinfo
command being inaccurate. This patch tries to avoid that by checking if
the topology actually makes sense. If it doesn't we then report a
synthetic topology that indicates to the user that the host capabilities
should be checked for the actual topology.

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index bf584a0bf602674aa8799a52a4733217b28220ee..49a361ae94994cbf645a7dc8b4e2a5d32ee3078b 100644 (file)
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -531,17 +531,19 @@ typedef virTypedParameter *virTypedParameterPtr;
 typedef struct _virNodeInfo virNodeInfo;
 
 struct _virNodeInfo {
-    char model[32];     /* string indicating the CPU model */
-    unsigned long memory;/* memory size in kilobytes */
-    unsigned int cpus;  /* the number of active CPUs */
-    unsigned int mhz;   /* expected CPU frequency */
-    unsigned int nodes; /* the number of NUMA cell, 1 for unusual NUMA
-                           topologies or uniform memory access; check
-                           capabilities XML for the actual NUMA topology */
-    unsigned int sockets;/* number of CPU sockets per node if nodes > 1,
-                            total number of CPU sockets otherwise */
-    unsigned int cores; /* number of cores per socket */
-    unsigned int threads;/* number of threads per core */
+    char model[32];       /* string indicating the CPU model */
+    unsigned long memory; /* memory size in kilobytes */
+    unsigned int cpus;    /* the number of active CPUs */
+    unsigned int mhz;     /* expected CPU frequency */
+    unsigned int nodes;   /* the number of NUMA cell, 1 for unusual NUMA
+                             topologies or uniform memory access; check
+                             capabilities XML for the actual NUMA topology */
+    unsigned int sockets; /* number of CPU sockets per node if nodes > 1,
+                             1 in case of unusual NUMA topology */
+    unsigned int cores;   /* number of cores per socket, total number of
+                             processors in case of unusual NUMA topology*/
+    unsigned int threads; /* number of threads per core, 1 in case of
+                             unusual numa topology */
 };
 
 /**

diff --git a/src/nodeinfo.c b/src/nodeinfo.c
index 36fbd66c7dc2b42a38b6bd8089dbc6fd175b0b99..e3d7cfeae41f3dee824b902dfaa1dad28be59359 100644 (file)
--- a/src/nodeinfo.c
+++ b/src/nodeinfo.c
@@ -204,7 +204,12 @@ CPU_COUNT(cpu_set_t *set)
 static int
 ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2)
 ATTRIBUTE_NONNULL(3) ATTRIBUTE_NONNULL(4)
-virNodeParseNode(const char *node, int *sockets, int *cores, int *threads)
+ATTRIBUTE_NONNULL(5)
+virNodeParseNode(const char *node,
+                 int *sockets,
+                 int *cores,
+                 int *threads,
+                 int *offline)
 {
     int ret = -1;
     int processors = 0;
@@ -278,8 +283,10 @@ virNodeParseNode(const char *node, int *sockets, int *cores, int *threads)
         if ((online = virNodeGetCpuValue(node, cpu, "online", true)) < 0)
             goto cleanup;
 
-        if (!online)
+        if (!online) {
+            (*offline)++;
             continue;
+        }
 
         processors++;
 
@@ -348,7 +355,7 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
     char line[1024];
     DIR *nodedir = NULL;
     struct dirent *nodedirent = NULL;
-    int cpus, cores, socks, threads;
+    int cpus, cores, socks, threads, offline = 0;
     unsigned int node;
     int ret = -1;
     char *sysfs_nodedir = NULL;
@@ -469,8 +476,8 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
             goto cleanup;
         }
 
-        if ((cpus = virNodeParseNode(sysfs_cpudir, &socks,
-                                     &cores, &threads)) < 0)
+        if ((cpus = virNodeParseNode(sysfs_cpudir, &socks, &cores,
+                                     &threads, &offline)) < 0)
             goto cleanup;
 
         VIR_FREE(sysfs_cpudir);
@@ -505,7 +512,8 @@ fallback:
         goto cleanup;
     }
 
-    if ((cpus = virNodeParseNode(sysfs_cpudir, &socks, &cores, &threads)) < 0)
+    if ((cpus = virNodeParseNode(sysfs_cpudir, &socks, &cores,
+                                 &threads, &offline)) < 0)
         goto cleanup;
 
     nodeinfo->nodes = 1;
@@ -531,6 +539,23 @@ done:
         goto cleanup;
     }
 
+    /* Now check if the topology makes sense. There are machines that don't
+     * expose their real number of nodes or for example the AMD Bulldozer
+     * architecture that exposes their Clustered integer core modules as both
+     * threads and cores. This approach throws off our detection. Unfortunately
+     * the nodeinfo structure isn't designed to carry the full topology so
+     * we're going to lie about the detected topology to notify the user
+     * to check the host capabilities for the actual topology. */
+    if ((nodeinfo->nodes *
+         nodeinfo->sockets *
+         nodeinfo->cores *
+         nodeinfo->threads) != (nodeinfo->cpus + offline)) {
+        nodeinfo->nodes = 1;
+        nodeinfo->sockets = 1;
+        nodeinfo->cores = nodeinfo->cpus + offline;
+        nodeinfo->threads = 1;
+    }
+
     ret = 0;
 
 cleanup: