Messages in this thread Patch in this message | | | Date | Tue, 18 Mar 2008 13:00:19 -0400 | From | Jeff Dike <> | Subject | Re: [2.6.24.x] UML select()/poll() oversleeping reproducibly |
| |
Below is another patch.
I was hurt and disappointed by your > Eeuuuuw. :) so I got rid of the 9/10 thing.
This version keeps track of the time between ticks (as reported by the host's gettimeofday) and adjusts its sleeping and reporting ticks accordingly.
It's still undersleeping a little - your little test once reported 19 seconds for a 20 second sleep. Otherwise, it's reporting sleep times that are right on the money.
Jeff
-- Work email - jdike at linux dot intel dot com
Index: linux-2.6.22/arch/um/os-Linux/time.c =================================================================== --- linux-2.6.22.orig/arch/um/os-Linux/time.c 2008-03-18 12:32:19.000000000 -0400 +++ linux-2.6.22/arch/um/os-Linux/time.c 2008-03-18 12:45:50.000000000 -0400 @@ -11,6 +11,7 @@ #include "kern_constants.h" #include "os.h" #include "user.h" +#include "kern_util.h" int set_interval(void) { @@ -58,12 +59,17 @@ static inline long long timeval_to_ns(co long long disable_timer(void) { struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } }); + int remain, max = UM_NSEC_PER_SEC / UM_HZ; if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0) printk(UM_KERN_ERR "disable_timer - setitimer failed, " "errno = %d\n", errno); - return timeval_to_ns(&time.it_value); + remain = timeval_to_ns(&time.it_value); + if (remain > max) + remain = max; + + return remain; } long long os_nsecs(void) @@ -79,7 +85,47 @@ static int after_sleep_interval(struct t { return 0; } + + +static void deliver_alarm(void) +{ + alarm_handler(SIGVTALRM, NULL); +} + +static unsigned long long sleep_time(unsigned long long nsecs) +{ + return nsecs; +} + #else +unsigned long long last_tick; +unsigned long long skew; + +extern void alarm_handler(int sig, struct sigcontext *sc); + +static void deliver_alarm(void) +{ + unsigned long long this_tick = os_nsecs(); + int one_tick = UM_NSEC_PER_SEC / UM_HZ; + + if (last_tick == 0) + last_tick = this_tick - one_tick; + + skew += this_tick - last_tick; + + while (skew >= one_tick) { + alarm_handler(SIGVTALRM, NULL); + skew -= one_tick; + } + + last_tick = this_tick; +} + +static unsigned long long sleep_time(unsigned long long nsecs) +{ + return nsecs > skew ? nsecs - skew : 0; +} + static inline long long timespec_to_us(const struct timespec *ts) { return ((long long) ts->tv_sec * UM_USEC_PER_SEC) + @@ -102,6 +148,8 @@ static int after_sleep_interval(struct t */ if (start_usecs > usec) start_usecs = usec; + + start_usecs -= skew / UM_NSEC_PER_USEC; tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC, .tv_usec = start_usecs % UM_USEC_PER_SEC }); interval = ((struct itimerval) { { 0, usec }, tv }); @@ -113,8 +161,6 @@ static int after_sleep_interval(struct t } #endif -extern void alarm_handler(int sig, struct sigcontext *sc); - void idle_sleep(unsigned long long nsecs) { struct timespec ts; @@ -126,10 +172,12 @@ void idle_sleep(unsigned long long nsecs */ if (nsecs == 0) nsecs = UM_NSEC_PER_SEC / UM_HZ; + + nsecs = sleep_time(nsecs); ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC, .tv_nsec = nsecs % UM_NSEC_PER_SEC }); if (nanosleep(&ts, &ts) == 0) - alarm_handler(SIGVTALRM, NULL); + deliver_alarm(); after_sleep_interval(&ts); }
| |