From: "Jakub W. Jozwicki" <jozwicki@aster.pl>
To: linux-kernel@vger.kernel.org
Subject: sched_yield() on 2.6.25
Date: Sun, 8 Jun 2008 13:34:10 +0200 [thread overview]
Message-ID: <200806081334.10875.jozwicki@aster.pl> (raw)
Hello,
I observe strange behavior of sched_yield() on 2.6.25 (strange comparing to
2.6.24). Here is the code (available at
http://systest.googlecode.com/files/systest20080119.tgz):
------------------------------------------------------
timer_t timer;
sig_atomic_t cnt = 0;
long long sum = 0;
long times[21], min, max;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
struct timespec ts = { 0, 0 };
pthread_t last_th = 0;
void *th_proc(void* p) {
int n = SIZE(times) -1;
pthread_t th;
while(1) {
pthread_mutex_lock(&mutex);
th = pthread_self();
if (pthread_equal(th,last_th)) {
pthread_mutex_unlock(&mutex);
sched_yield();
continue;
}
rt_timer_stop(&ts);
last_th = th;
if (cnt>=1) {
times[cnt-1] = ts_sum(&ts);
if (cnt <= n) {
sum += times[cnt-1];
box(times[cnt-1],min,max);
#define uint unsigned int
printf("[%u] Thread switching time: %ldns\n",(uint)th, times[cnt-1]);
}
else {
printf("[%u] Thread switching time (not counted): %ldns\n",(uint)th,
times[cnt-1]);
}
cnt--;
}
....
-----------------------------------------------------
and here are the results:
Setting cpu mask to 1
-- SYSTEM INFO -------------------
localhost: Linux 2.6.24-rt4 #8 SMP PREEMPT RT Mon Jan 21 18:45:00 CET 2008
Setting priority SCHED_OTHER to 0 (normal process) for 20802
[3084102544] Thread switching time (not counted): 10709015ns
[3075709840] Thread switching time: 35468301ns
[3084102544] Thread switching time: 2793ns
[3075709840] Thread switching time 30725ns
[3084102544] Thread switching time: 10405ns
[3075709840] Thread switching time: 2724ns
[3084102544] Thread switching time: 2654ns
[3075709840] Thread switching time: 2653ns
[3084102544] Thread switching time: 3352ns
[3075709840] Thread switching time: 2583ns
[3084102544] Thread switching time: 2514ns
[3075709840] Thread switching time: 2514ns
[3084102544] Thread switching time: 2584ns
[3075709840] Thread switching time: 2584ns
[3084102544] Thread switching time: 2584ns
[3075709840] Thread switching time: 2584ns
[3084102544] Thread switching time: 2584ns
[3075709840] Thread switching time: 2584ns
[3084102544] Thread switching time: 2583ns
[3075709840] Thread switching time: 2584ns
[3084102544] Thread switching time: 2583ns
[3084102544] n=20, min=2514, max=35468301, avg=1777723, stddev=7729151
Setting priority SHED_FIFO to 99 (range is 1-99) for 20802
[3084102544] Thread switching time (not counted): 31004ns
[3075709840] Thread switching time: 2444ns
[3084102544] Thread switching time: 2305ns
[3075709840] Thread switching time: 2305ns
[3084102544] Thread switching time: 2374ns
[3075709840] Thread switching time: 2374ns
[3084102544] Thread switching time: 2374ns
[3075709840] Thread switching time: 2375ns
[3084102544] Thread switching time: 2305ns
[3075709840] Thread switching time: 2374ns
[3084102544] Thread switching time: 2305ns
[3075709840] Thread switching time: 2375ns
[3084102544] Thread switching time: 2305ns
[3075709840] Thread switching time: 2305ns
[3084102544] Thread switching time: 2305ns
[3075709840] Thread switching time: 2305ns
[3084102544] Thread switching time: 2304ns
[3075709840] Thread switching time: 2304ns
[3084102544] Thread switching time: 2374ns
[3075709840] Thread switching time: 2374ns
[3084102544] Thread switching time: 2304ns
[3084102544] n=20, min=2304, max=2444, avg=2339, stddev=41
--------------------------------------------------------------------------
Ustawianie maski procesorow na 1
-- SYSTEM INFO -------------------
hackett: Linux 2.6.25.4-rt6 #5 SMP PREEMPT RT Sun Jun 8 12:40:15 CEST 2008
Ustawianie priorytetu dla SCHED_OTHER na 0 (zwykly proces) dla 20511
[3085323152] Czas przelaczania watku (pomijany): 9286166ns
[3076930448] Czas przelaczania watku: 38678449ns
[3085323152] Czas przelaczania watku: 1181784ns
[3076930448] Czas przelaczania watku: 284114ns
[3085323152] Czas przelaczania watku: 2894642ns
[3076930448] Czas przelaczania watku: 975962ns
[3085323152] Czas przelaczania watku: 2010730ns
[3076930448] Czas przelaczania watku: 980292ns
[3085323152] Czas przelaczania watku: 2004934ns
[3076930448] Czas przelaczania watku: 983994ns
[3085323152] Czas przelaczania watku: 2009682ns
[3076930448] Czas przelaczania watku: 984343ns
[3085323152] Czas przelaczania watku: 2013036ns
[3076930448] Czas przelaczania watku: 979035ns
[3085323152] Czas przelaczania watku: 2013664ns
[3076930448] Czas przelaczania watku: 973727ns
[3085323152] Czas przelaczania watku: 1688204ns
[3076930448] Czas przelaczania watku: 309397ns
[3085323152] Czas przelaczania watku: 985181ns
[3076930448] Czas przelaczania watku: 997822ns
[3085323152] Czas przelaczania watku: 996495ns
[3085323152] n=20, min=284114, max=38678449, avg=3197274, stddev=8164859
Ustawianie priorytetu dla SHED_FIFO na 99 (zakres 1-99) dla 20511
[3085323152] Czas przelaczania watku (pomijany): 39740ns
[3076930448] Czas przelaczania watku: 2723ns
[3085323152] Czas przelaczania watku: 2444ns
[3076930448] Czas przelaczania watku: 2445ns
[3085323152] Czas przelaczania watku: 2444ns
[3076930448] Czas przelaczania watku: 2445ns
[3085323152] Czas przelaczania watku: 2444ns
[3076930448] Czas przelaczania watku: 2445ns
[3085323152] Czas przelaczania watku: 2375ns
[3076930448] Czas przelaczania watku: 2445ns
[3085323152] Czas przelaczania watku: 2375ns
[3076930448] Czas przelaczania watku: 2375ns
[3085323152] Czas przelaczania watku: 2444ns
[3076930448] Czas przelaczania watku: 2374ns
[3085323152] Czas przelaczania watku: 2375ns
[3076930448] Czas przelaczania watku: 2375ns
[3085323152] Czas przelaczania watku: 2445ns
[3076930448] Czas przelaczania watku: 2444ns
[3085323152] Czas przelaczania watku: 2375ns
[3076930448] Czas przelaczania watku: 2374ns
[3085323152] Czas przelaczania watku: 2445ns
[3085323152] n=20, min=2374, max=2723, avg=2430, stddev=75
Is this behavior expected?
Regards,
Jakub
next reply other threads:[~2008-06-08 11:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-08 11:34 Jakub W. Jozwicki [this message]
2008-06-09 9:35 ` sched_yield() on 2.6.25 Andrew Morton
[not found] <fa.5iKTy3xTJkKWZLGio+GIHXi3+0o@ifi.uio.no>
2008-06-08 22:09 ` Robert Hancock
2008-06-09 6:37 ` Jakub Jozwicki
2008-06-09 9:03 ` Helge Hafting
2008-06-09 15:04 ` Peter Zijlstra
[not found] <aCBfw-3Cv-23@gated-at.bofh.it>
[not found] ` <aCBfw-3Cv-21@gated-at.bofh.it>
[not found] ` <aCJd6-3IF-11@gated-at.bofh.it>
[not found] ` <aCRaM-8cM-33@gated-at.bofh.it>
2008-06-11 15:28 ` Bodo Eggert
2008-06-11 22:45 ` Leon Woestenberg
2008-06-12 8:09 ` Helge Hafting
2008-06-12 22:33 ` Bodo Eggert
2008-06-13 8:37 ` Helge Hafting
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