[PATCH] libnuma: don't cache node cpumasks older than 1 second

To preserve useful caching feature and minimize the risk of getting outdated
node cpumask after cpu hotplugging, numactl refreshes cache for every call
delayed more as one second from previous one. This is compromise between
outdated static cache and node cpumask parsing during every call of
numa_node_to_cpus which would be very inefficient.

Signed-off-by: Petr Holasek <[email protected]>
---
 libnuma.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libnuma.c b/libnuma.c
index 3717d5b..30d4ac8 100644
--- a/libnuma.c
+++ b/libnuma.c
@@ -30,6 +30,7 @@
 
 #include <sys/mman.h>
 #include <limits.h>
+#include <time.h>
 
 #include "config.h"
 #include "numa.h"
@@ -76,6 +77,7 @@ static int numprocnode = -1;
 static int numproccpu = -1;
 static int nodemask_sz = 0;
 static int cpumask_sz = 0;
+static time_t last_tstamp = 0;
 
 int numa_exit_on_error = 0;
 int numa_exit_on_warn = 0;
@@ -1328,6 +1330,7 @@ numa_node_to_cpus_v2(int node, struct bitmask *buffer)
 	FILE *f; 
 	size_t len = 0; 
 	struct bitmask *mask;
+	time_t curr_tstamp;
 
 	if (!node_cpu_mask_v2)
 		init_node_cpu_mask_v2();
@@ -1338,7 +1341,9 @@ numa_node_to_cpus_v2(int node, struct bitmask *buffer)
 	}
 	numa_bitmask_clearall(buffer);
 
-	if (node_cpu_mask_v2[node]) {
+	curr_tstamp = time(NULL);
+
+	if (node_cpu_mask_v2[node] && curr_tstamp == last_tstamp) {
 		/* have already constructed a mask for this node */
 		if (buffer->size < node_cpu_mask_v2[node]->size) {
 			numa_error("map size mismatch; abort\n");
@@ -1388,6 +1393,9 @@ numa_node_to_cpus_v2(int node, struct bitmask *buffer)
 		else
 			numa_bitmask_free(mask);
 	}
+
+	last_tstamp = curr_tstamp;
+
 	return err; 
 }
 __asm__(".symver numa_node_to_cpus_v2,numa_node_to_cpus@@libnuma_1.2");
-- 
2.4.3