selftests/powerpc: context_switch use private futexes with threads

This reduces overhead of mutex locking and increases context switch
rate significantly (which helps to measure and profile the context
switch path).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/tools/testing/selftests/powerpc/benchmarks/context_switch.c b/tools/testing/selftests/powerpc/benchmarks/context_switch.c
index 778f5fbfd784a3e335cd30adf029640d97c3a90b..f4241339edd2a1ba9b449fb1ebab184075c0378d 100644 (file)
--- a/tools/testing/selftests/powerpc/benchmarks/context_switch.c
+++ b/tools/testing/selftests/powerpc/benchmarks/context_switch.c
@@ -258,9 +258,14 @@ static unsigned long xchg(unsigned long *p, unsigned long val)
        return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
 }
 
+static int processes;
+
 static int mutex_lock(unsigned long *m)
 {
        int c;
+       int flags = FUTEX_WAIT;
+       if (!processes)
+               flags |= FUTEX_PRIVATE_FLAG;
 
        c = cmpxchg(m, 0, 1);
        if (!c)
@@ -270,7 +275,7 @@ static int mutex_lock(unsigned long *m)
                c = xchg(m, 2);
 
        while (c) {
-               sys_futex(m, FUTEX_WAIT, 2, NULL, NULL, 0);
+               sys_futex(m, flags, 2, NULL, NULL, 0);
                c = xchg(m, 2);
        }
 
@@ -279,12 +284,16 @@ static int mutex_lock(unsigned long *m)
 
 static int mutex_unlock(unsigned long *m)
 {
+       int flags = FUTEX_WAKE;
+       if (!processes)
+               flags |= FUTEX_PRIVATE_FLAG;
+
        if (*m == 2)
                *m = 0;
        else if (xchg(m, 0) == 1)
                return 0;
 
-       sys_futex(m, FUTEX_WAKE, 1, NULL, NULL, 0);
+       sys_futex(m, flags, 1, NULL, NULL, 0);
 
        return 0;
 }
@@ -293,26 +302,32 @@ static unsigned long *m1, *m2;
 
 static void futex_setup(int cpu1, int cpu2)
 {
-       int shmid;
-       void *shmaddr;
+       if (!processes) {
+               static unsigned long _m1, _m2;
+               m1 = &_m1;
+               m2 = &_m2;
+       } else {
+               int shmid;
+               void *shmaddr;
 
-       shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
-       if (shmid < 0) {
-               perror("shmget");
-               exit(1);
-       }
+               shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
+               if (shmid < 0) {
+                       perror("shmget");
+                       exit(1);
+               }
 
-       shmaddr = shmat(shmid, NULL, 0);
-       if (shmaddr == (char *)-1) {
-               perror("shmat");
-               shmctl(shmid, IPC_RMID, NULL);
-               exit(1);
-       }
+               shmaddr = shmat(shmid, NULL, 0);
+               if (shmaddr == (char *)-1) {
+                       perror("shmat");
+                       shmctl(shmid, IPC_RMID, NULL);
+                       exit(1);
+               }
 
-       shmctl(shmid, IPC_RMID, NULL);
+               shmctl(shmid, IPC_RMID, NULL);
 
-       m1 = shmaddr;
-       m2 = shmaddr + sizeof(*m1);
+               m1 = shmaddr;
+               m2 = shmaddr + sizeof(*m1);
+       }
 
        *m1 = 0;
        *m2 = 0;
@@ -352,8 +367,6 @@ static struct actions futex_actions = {
        .thread2 = futex_thread2,
 };
 
-static int processes;
-
 static struct option options[] = {
        { "test", required_argument, 0, 't' },
        { "process", no_argument, &processes, 1 },