From b27ce776852078df9e14a223b375db6507096963 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sun, 4 Jun 2017 22:06:22 +1000 Subject: [PATCH] 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 Signed-off-by: Michael Ellerman --- .../powerpc/benchmarks/context_switch.c | 53 ++++++++++++------- 1 file changed, 33 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/powerpc/benchmarks/context_switch.c b/tools/testing/selftests/powerpc/benchmarks/context_switch.c index 778f5fbfd784..f4241339edd2 100644 --- 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 }, -- 2.20.1