Fix: numa: dynamically check that numa is available

Kernels with CONFIG_NUMA=n cause libnuma to print those messages:

"set_mempolicy: Function not implemented".

Check for numa availability before using it.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 0153578c93a2cfddf3bdd69ae57324b516086651..10b3bcef110a979ce2169ccf10417e470e122ba9 100644 (file)
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -33,8 +33,10 @@
 #include <dirent.h>
 #include <lttng/align.h>
 #include <limits.h>
+#include <stdbool.h>
 #ifdef HAVE_LIBNUMA
 #include <numa.h>
+#include <numaif.h>
 #endif
 #include <helper.h>
 #include <ust-fd.h>
@@ -244,6 +246,24 @@ alloc_error:
        return NULL;
 }
 
+/*
+ * libnuma prints errors on the console even for numa_available().
+ * Work-around this limitation by using get_mempolicy() directly to
+ * check whether the kernel supports mempolicy.
+ */
+#ifdef HAVE_LIBNUMA
+static bool lttng_is_numa_available(void)
+{
+       int ret;
+
+       ret = get_mempolicy(NULL, NULL, 0, NULL, 0);
+       if (ret && errno == ENOSYS) {
+               return false;
+       }
+       return numa_available() > 0;
+}
+#endif
+
 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
                        size_t memory_map_size,
                        enum shm_object_type type,
@@ -252,16 +272,20 @@ struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
 {
        struct shm_object *shm_object;
 #ifdef HAVE_LIBNUMA
-       int oldnode, node;
-
-       oldnode = numa_preferred();
-       if (cpu >= 0) {
-               node = numa_node_of_cpu(cpu);
-               if (node >= 0)
-                       numa_set_preferred(node);
+       int oldnode = 0, node;
+       bool numa_avail;
+
+       numa_avail = lttng_is_numa_available();
+       if (numa_avail) {
+               oldnode = numa_preferred();
+               if (cpu >= 0) {
+                       node = numa_node_of_cpu(cpu);
+                       if (node >= 0)
+                               numa_set_preferred(node);
+               }
+               if (cpu < 0 || node < 0)
+                       numa_set_localalloc();
        }
-       if (cpu < 0 || node < 0)
-               numa_set_localalloc();
 #endif /* HAVE_LIBNUMA */
        switch (type) {
        case SHM_OBJECT_SHM:
@@ -275,7 +299,8 @@ struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
                assert(0);
        }
 #ifdef HAVE_LIBNUMA
-       numa_set_preferred(oldnode);
+       if (numa_avail)
+               numa_set_preferred(oldnode);
 #endif /* HAVE_LIBNUMA */
        return shm_object;
 }