diff mbox series

[v3,2/2] Add single-threaded fast path to rand()

Message ID PAWPR08MB89822B28BED09B70092067EB838DA@PAWPR08MB8982.eurprd08.prod.outlook.com
State New
Headers show
Series [v3,1/2] Add random benchmark | expand

Commit Message

Wilco Dijkstra Dec. 13, 2023, 2:10 p.m. UTC 
Improve performance of rand() and __random() by adding a single-threaded fast
path.  Bench-random-lock shows about 5x speedup on Neoverse V1.

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Patch

diff --git a/stdlib/random.c b/stdlib/random.c
index 62f22fac8d58c7977f09c134bf80a797750da645..174603a8915fd8aa4b3ae64d023003c9e2c038f2 100644
--- a/stdlib/random.c
+++ b/stdlib/random.c
@@ -51,6 +51,7 @@ 
    SUCH DAMAGE.*/
 
 #include <libc-lock.h>
+#include <sys/single_threaded.h>
 #include <limits.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ -288,6 +289,12 @@  __random (void)
 {
   int32_t retval;
 
+  if (SINGLE_THREAD_P)
+    {
+      (void) __random_r (&unsafe_state, &retval);
+      return retval;
+    }
+
   __libc_lock_lock (lock);
 
   (void) __random_r (&unsafe_state, &retval);