nodeinfo: drop static variable

We were wasting time to malloc a copy of a constant string, then
copy it into static storage, for every call to nodeGetInfo.  At
least we were lucky that it was a constant source, and thus not
subject to even worse issues with one thread clobbering the static
storage while another was using it.  This gets rid of the waste,
by passing the string through the stack instead, as well as renaming
internal functions to better match our conventions.

* src/nodeinfo.c (sysfs_path): Delete.
(get_cpu_value, count_thread_siblings, parse_socket): Add
parameter, and rename...
(virNodeGetCpuValue, virNodeCountThreadSiblings)
(virNodeParseSocket): ... into a common namespace.
(cpu_online, parse_core): Inline into callers.
(linuxNodeInfoCPUPopulate): Update caller.
(nodeGetInfo): Drop a useless malloc.

src/nodeinfo.c

@@ -81,14 +81,14 @@ static int linuxNodeGetMemoryStats(FILE *meminfo,
                                    virNodeMemoryStatsPtr params,
                                    int *nparams);
 
-static char sysfs_path[1024];
 /* Return the positive decimal contents of the given
- * (*sysfs_path)/cpu%u/FILE, or -1 on error.  If MISSING_OK and the
+ * DIR/cpu%u/FILE, or -1 on error.  If MISSING_OK and the
  * file could not be found, return 1 instead of an error; this is
  * because some machines cannot hot-unplug cpu0, or because
  * hot-unplugging is disabled.  */
 static int
-get_cpu_value(unsigned int cpu, const char *file, bool missing_ok)
+virNodeGetCpuValue(const char *dir, unsigned int cpu, const char *file,
+                   bool missing_ok)
 {
     char *path;
     FILE *pathfp;
@@ -96,7 +96,7 @@ get_cpu_value(unsigned int cpu, const char *file, bool missing_ok)
     char value_str[INT_BUFSIZE_BOUND(value)];
     char *tmp;
 
-    if (virAsprintf(&path, "%s/cpu%u/%s", sysfs_path, cpu, file) < 0) {
+    if (virAsprintf(&path, "%s/cpu%u/%s", dir, cpu, file) < 0) {
         virReportOOMError();
         return -1;
     }
@@ -128,15 +128,8 @@ cleanup:
     return value;
 }
 
-/* Check if CPU is online via sysfs_path/cpu%u/online.  Return 1 if online,
-   0 if offline, and -1 on error.  */
-static int
-cpu_online(unsigned int cpu)
-{
-    return get_cpu_value(cpu, "online", true);
-}
-
-static unsigned long count_thread_siblings(unsigned int cpu)
+static unsigned long
+virNodeCountThreadSiblings(const char *dir, unsigned int cpu)
 {
     unsigned long ret = 0;
     char *path;
@@ -145,7 +138,7 @@ static unsigned long count_thread_siblings(unsigned int cpu)
     int i;
 
     if (virAsprintf(&path, "%s/cpu%u/topology/thread_siblings",
-                    sysfs_path, cpu) < 0) {
+                    dir, cpu) < 0) {
         virReportOOMError();
         return 0;
     }
@@ -180,9 +173,11 @@ cleanup:
     return ret;
 }
 
-static int parse_socket(unsigned int cpu)
+static int
+virNodeParseSocket(const char *dir, unsigned int cpu)
 {
-    int ret = get_cpu_value(cpu, "topology/physical_package_id", false);
+    int ret = virNodeGetCpuValue(dir, cpu, "topology/physical_package_id",
+                                 false);
 # if defined(__powerpc__) || \
     defined(__powerpc64__) || \
     defined(__s390__) || \
@@ -194,11 +189,6 @@ static int parse_socket(unsigned int cpu)
     return ret;
 }
 
-static int parse_core(unsigned int cpu)
-{
-    return get_cpu_value(cpu, "topology/core_id", false);
-}
-
 int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
                              const char *sysfs_cpudir,
                              virNodeInfoPtr nodeinfo)
@@ -222,10 +212,6 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
         nodeinfo->nodes = numa_max_node() + 1;
 # endif
 
-    if (!virStrcpyStatic(sysfs_path, sysfs_cpudir)) {
-        virReportSystemError(errno, _("cannot copy %s"), sysfs_cpudir);
-        return -1;
-    }
     /* NB: It is impossible to fill our nodes, since cpuinfo
      * has no knowledge of NUMA nodes */
 
@@ -296,7 +282,7 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
         if (sscanf(cpudirent->d_name, "cpu%u", &cpu) != 1)
             continue;
 
-        online = cpu_online(cpu);
+        online = virNodeGetCpuValue(sysfs_cpudir, cpu, "online", true);
         if (online < 0) {
             closedir(cpudir);
             return -1;
@@ -306,20 +292,20 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
         nodeinfo->cpus++;
 
         /* Parse core */
-        core = parse_core(cpu);
+        core = virNodeGetCpuValue(sysfs_cpudir, cpu, "topology/core_id", false);
         if (!CPU_ISSET(core, &core_mask)) {
             CPU_SET(core, &core_mask);
             nodeinfo->cores++;
         }
 
         /* Parse socket */
-        sock = parse_socket(cpu);
+        sock = virNodeParseSocket(sysfs_cpudir, cpu);
         if (!CPU_ISSET(sock, &socket_mask)) {
             CPU_SET(sock, &socket_mask);
             nodeinfo->sockets++;
         }
 
-        cur_threads = count_thread_siblings(cpu);
+        cur_threads = virNodeCountThreadSiblings(sysfs_cpudir, cpu);
         if (cur_threads == 0) {
             closedir(cpudir);
             return -1;
@@ -329,7 +315,7 @@ int linuxNodeInfoCPUPopulate(FILE *cpuinfo,
     }
     if (errno) {
         virReportSystemError(errno,
-                             _("problem reading %s"), sysfs_path);
+                             _("problem reading %s"), sysfs_cpudir);
         closedir(cpudir);
         return -1;
     }
@@ -627,7 +613,6 @@ int nodeGetInfo(virConnectPtr conn ATTRIBUTE_UNUSED, virNodeInfoPtr nodeinfo) {
 #ifdef __linux__
     {
     int ret = -1;
-    char *sysfs_cpuinfo = NULL;
     FILE *cpuinfo = fopen(CPUINFO_PATH, "r");
     if (!cpuinfo) {
         virReportSystemError(errno,
@@ -635,12 +620,7 @@ int nodeGetInfo(virConnectPtr conn ATTRIBUTE_UNUSED, virNodeInfoPtr nodeinfo) {
         return -1;
     }
 
-    if (virAsprintf(&sysfs_cpuinfo, CPU_SYS_PATH) < 0) {
-        virReportOOMError();
-        goto cleanup;
-    }
-
-    ret = linuxNodeInfoCPUPopulate(cpuinfo, sysfs_cpuinfo, nodeinfo);
+    ret = linuxNodeInfoCPUPopulate(cpuinfo, CPU_SYS_PATH, nodeinfo);
     if (ret < 0)
         goto cleanup;
 
@@ -649,7 +629,6 @@ int nodeGetInfo(virConnectPtr conn ATTRIBUTE_UNUSED, virNodeInfoPtr nodeinfo) {
 
 cleanup:
     VIR_FORCE_FCLOSE(cpuinfo);
-    VIR_FREE(sysfs_cpuinfo);
     return ret;
     }
 #else