Date: Sun, 22 Sep 1996 17:06:25 -0700 From: Julian Elischer <julian@whistle.com> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-bugs@freefall.freebsd.org Subject: Re: kern/1652: Version of itimer patch for -current Message-ID: <3245D481.7566F4CF@whistle.com> References: <199609200220.TAA04571@freefall.freebsd.org>
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Bruce Evans wrote:
> From: Bruce Evans <bde@zeta.org.au>
[...]
> >It is possible that this should only be called if delta is greater than a particular
> >size.
>
> No, delta is very unlikely to be small (else adjtime() should have
[...]
Ok so that part stays the same.. no such optimisation..
>
> >Also SPL must be considered if the number of processes is large..
>
> Yes, walking the queue at splclock() defeats the micro-optimized spl
> placement in settimeofday(). It think atomic update is only
> necessary for each itimer, not for all of them together.
hmm do you think we need any particular locking then?
will we break SMP stuff?
etc. etc.
would doing it a splsoftclock be sufficient?
if so, how about the fix below?
do we need to lock the process list for SMP ops?
>
> >I could check this in myself, but I want comments first..
>
> Mihoko Tanaka <mihoko@pa.yokogawa.co.jp> posted a similar fix
> the other day.
yes and I think we need to do this..
>
> All versions forgot to remove or update the load comment about
> this problem.
eh?
Oh you mean the comment in the code?
yeah ok, if I did this I'd change the comment.. :-)
>
> I wonder why this problem has been around for so long, and why
> adjkerntz doesn't seem to cause it.
sorry I don't follow..
adjkerntz?
that doesn't change the internal time does it?
just how we express it?
Oh I see, because we interpret the cmos clock differntly..?
well that will only be at most 24 hours, or 3600x24 loops.
Where we are talking about year sized changes..
>
> Bruce
o
how about the following variation? (using splsoftclock)
(warning.. cut+paste used)
*** 1.17 1996/07/12 07:55:35
--- kern_time.c 1996/09/23 00:04:46
***************
*** 56,61 ****
--- 56,62 ----
*/
static void timevalfix __P((struct timeval *));
+ static void recalc_realtimer(struct timeval);
#ifndef _SYS_SYSPROTO_H_
struct gettimeofday_args {
***************
*** 114,120 ****
(error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
sizeof(atz))))
return (error);
if (uap->tv) {
- /* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
s = splclock();
/*
* Calculate delta directly to minimize clock interrupt
--- 115,120 ----
***************
*** 136,141 ****
--- 136,142 ----
timevalfix(&delta);
timevaladd(&boottime, &delta);
timevaladd(&runtime, &delta);
+ recalc_realtimer(delta);
LEASE_UPDATETIME(delta.tv_sec);
splx(s);
resettodr();
***************
*** 144,149 ****
--- 145,164 ----
tz = atz;
return (0);
}
+
+
+ static void
+ recalc_realtimer(struct timeval delta)
+ {
+ struct proc *p;
+
+ for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
+ if (timerisset(&p->p_realtimer.it_value)) {
+ timevaladd(&p->p_realtimer.it_value, &delta);
+ timevalfix(&p->p_realtimer.it_value);
+ }
+ }
+ }
extern int tickadj; /* "standard" clock
skew, us./tick */
int tickdelta; /* current clock skew, us. per
tick */
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