From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 5 Dec 2017 16:55:07 +0000 (-0500)
Subject: Fix: numa: dynamically check that numa is available
X-Git-Tag: v2.11.0-rc1~29
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=8a208943e21700211beee3ea64180a5a534c7d2a

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 0153578c..10b3bcef 100644
--- 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;
 }