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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>
This commit is contained in:
Nicholas Piggin 2017-06-04 22:06:22 +10:00 committed by Michael Ellerman
parent b802ab46ba
commit b27ce77685
1 changed files with 33 additions and 20 deletions
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21
tools/testing/selftests/powerpc/benchmarks/context_switch.c
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@ -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;
}
@ -293,6 +302,11 @@ static unsigned long *m1, *m2;
static void futex_setup(int cpu1, int cpu2)
{
if (!processes) {
static unsigned long _m1, _m2;
m1 = &_m1;
m2 = &_m2;
} else {
int shmid;
void *shmaddr;
@ -313,6 +327,7 @@ static void futex_setup(int cpu1, int cpu2)
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 },