* Con Kolivas <[email protected]> [050901 08:22]:
> On Thu, 1 Sep 2005 02:58 am, Srivatsa Vaddagiri wrote:
> > Following patches related to dynamic tick are posted in separate mails,
> > for convenience of review. The first patch probably applies w/o dynamic
> > tick consideration also.
> >
> > Patch 1/3 -> Fixup lost tick calculation in timer_pm.c
> > Patch 2/3 -> Dyn-tick cleanups
> > Patch 3/3 -> Use lost tick information in dyn-tick time recovery
> >
> > These patches are against 2.6.13-rc6-mm2.
> >
> > Con, would be great if you can upload a consolidated new version of
> > dyn-tick patch on your website!
>
> Great, thanks. I'll wait till 2.6.13-mm1 is out since that's due shortly and
> I'll resync everything with that and perhaps tweak along the way.
I tried this quickly on a loaner ThinkPad T30, and needed the following
patch to compile. The patch does work with PIT, but with lapic the
system does not wake to timer interrupts :(
I also hacked together a little timer test utility that should go trough
on a completely idle system with no errors. Also posted it to:
http://www.muru.com/linux/dyntick/tools/dyntick-test.c
Srivatsa, could you try the dyntick-test.c on your system after booting
to init=/bin/sh to make the system as idle as possible?
Unfortunately I cannot debug the APIC issue right now, but I seem to
have an issue on ARM OMAP where the timer test occasionally fails on
some longer values, for example 3 second sleep can take 4 seconds.
I don't know yet if this is the problem George Anzinger mentioned with
next_timer_interrupt(), or if this is OMAP specific. But it only seems
to occur with very low idle HZ values. This may be related to the slow
boot time issue I mentioned yesterday.
Regards,
Tony
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -2034,7 +2034,9 @@
.disable = mask_IO_APIC_irq,
.ack = ack_edge_ioapic,
.end = end_edge_ioapic,
+#ifdef CONFIG_SMP
.set_affinity = set_ioapic_affinity,
+#endif
};
#endif
/*
* Tests timers to make sure dynamic tick works properly
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#define MAX_SLEEP (10) /* seconds */
#define MAX_LATENCY (100 * 1000) /* usecs */
int test_sleep(unsigned int msec_len)
{
sleep(msec_len / 1000);
return 0;
}
int test_select(unsigned int msec_len)
{
struct timeval tv_sel;
tv_sel.tv_sec = msec_len / 1000;
tv_sel.tv_usec = (msec_len % 1000) * 1000;
return select(0, NULL, NULL, NULL, &tv_sel);
}
int test_usleep(unsigned int msec_len)
{
usleep(msec_len * 1000);
}
/* This modified from some GNU exsample _not_ to hose y */
int timeval_subtract(struct timeval *result,
const struct timeval *x,
const struct timeval *y)
{
struct timeval tmp;
tmp.tv_sec = y->tv_sec;
tmp.tv_usec = y->tv_usec;
/* Perform the carry for the later subtraction */
if (x->tv_usec < y->tv_usec) {
int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
tmp.tv_usec -= 1000000 * nsec;
tmp.tv_sec += nsec;
}
if (x->tv_usec - y->tv_usec > 1000000) {
int nsec = (x->tv_usec - y->tv_usec) / 1000000;
tmp.tv_usec += 1000000 * nsec;
tmp.tv_sec -= nsec;
}
/* Compute the time remaining to wait.
tv_usec is certainly positive. */
result->tv_sec = x->tv_sec - tmp.tv_sec;
result->tv_usec = x->tv_usec - tmp.tv_usec;
/* Return 1 if result is negative. */
return x->tv_sec < tmp.tv_sec;
}
int do_test(char * name, int (* test)(unsigned int len),
unsigned int len, int count)
{
int i, ret;
struct timeval tv_in;
struct timeval tv_beg;
struct timeval tv_end;
struct timeval tv_len;
struct timeval tv_lat;
struct timezone tz;
char * status = "OK";
char * latency_type = "";
tv_in.tv_sec = len / 1000;
tv_in.tv_usec = (len % 1000) * 1000;
gettimeofday(&tv_beg, &tz);
for (i = 0; i < count; i++) {
ret = test(len);
}
gettimeofday(&tv_end, &tz);
ret = timeval_subtract(&tv_len, &tv_end, &tv_beg);
if (ret)
status = "ERROR";
ret = timeval_subtract(&tv_lat, &tv_len, &tv_in);
if (ret) {
latency_type = "-";
timeval_subtract(&tv_lat, &tv_in, &tv_len);
}
if (tv_lat.tv_sec > 0 || tv_lat.tv_usec > MAX_LATENCY)
status = "ERROR";
printf(" Test: %6s %4ums time: %2u.%06us "
"latency: %1s%u.%06us status: %s\n",
name,
(len * count),
(unsigned int)tv_len.tv_sec,
(unsigned int)tv_len.tv_usec,
latency_type,
(unsigned int)tv_lat.tv_sec,
(unsigned int)tv_lat.tv_usec,
status);
return ret;
}
int main(void)
{
unsigned int i;
int max_secs = MAX_SLEEP;
printf("Testing sub-second select and usleep\n");
for (i = 0; i < 1000; i += 100) {
do_test("select", test_select, i, 1);
do_test("usleep", test_usleep, i, 1);
}
printf("Testing multi-second select and sleep\n");
for (i = 0; i < max_secs; i++) {
do_test("select", test_select, i * 1000, 1);
do_test("sleep", test_sleep, i * 1000, 1);
}
return 0;
}
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