Always update a stats file in a subdirectory to reduce lock contention

diff --git a/stats.c b/stats.c
index 2c854c27ec7e4fd27c71f519d792fcd13ffa19c7..841e97c5d124d697e481898ac546c1d7496bb9d5 100644 (file)
--- a/stats.c
+++ b/stats.c
@@ -23,6 +23,7 @@
  */
 
 #include "ccache.h"
+#include "hashutil.h"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -176,13 +177,17 @@ void stats_flush(void)
        if (!should_flush) return;
 
        if (!stats_file) {
+               char *stats_dir;
+
                /*
                 * A NULL stats_file means that we didn't get past calculate_object_hash(),
-                * so we update the counter in the cache-wide statistics file
-                * CCACHE_DIR/stats instead of a subdirectory stats file.
+                * so we just choose one of stats files in the 16 subdirectories.
                 */
                if (!cache_dir) return;
-               stats_file = format("%s/stats", cache_dir);
+               stats_dir = format("%s/%x", cache_dir, hash_from_int(getpid()) % 16);
+               stats_file = format("%s/stats", stats_dir);
+               create_dir(stats_dir);
+               free(stats_dir);
        }
 
        fd = safe_open(stats_file);