Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-25 12:21:37 +00:00
Code Issues Packages Projects Releases Wiki Activity

selftests/powerpc: context_switch use private futexes with threads

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
tools/testing/selftests/powerpc/benchmarks/context_switch.c
View File

@ -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;
}
@ -293,27 +302,33 @@ 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);
m1 = shmaddr;
m2 = shmaddr + sizeof(*m1);
}
shmctl(shmid, IPC_RMID, NULL);
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 },