Date: Thu, 24 Jun 2004 20:12:07 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: current@freebsd.org Subject: fix for calcru() on running non-current threads Message-ID: <20040624201018.L41701@gamplex.bde.org>
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Accessing switchtime for other CPUs turned out to be easy.
Please test and review. (Tests should show no difference for the non-SMP
case.)
%%%
Index: kern_resource.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_resource.c,v
retrieving revision 1.140
diff -u -2 -r1.140 kern_resource.c
--- kern_resource.c 21 Jun 2004 17:46:27 -0000 1.140
+++ kern_resource.c 24 Jun 2004 07:31:05 -0000
@@ -48,4 +48,5 @@
#include <sys/malloc.h>
#include <sys/mutex.h>
+#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
@@ -707,5 +708,5 @@
/* {user, system, interrupt, total} {ticks, usec}; previous tu: */
u_int64_t ut, uu, st, su, it, iu, tt, tu, ptu;
- int problemcase;
+ int bt_valid;
mtx_assert(&sched_lock, MA_OWNED);
@@ -722,27 +723,20 @@
}
rt = p->p_runtime;
- problemcase = 0;
+ bt_valid = 0;
FOREACH_THREAD_IN_PROC(p, td) {
- /*
- * Adjust for the current time slice. This is actually fairly
- * important since the error here is on the order of a time
- * quantum, which is much greater than the sampling error.
- */
- if (td == curthread) {
- binuptime(&bt);
- bintime_sub(&bt, PCPU_PTR(switchtime));
- bintime_add(&rt, &bt);
- } else if (TD_IS_RUNNING(td)) {
+ if (TD_IS_RUNNING(td)) {
/*
- * XXX: this case should add the difference between
- * the current time and the switch time as above,
- * but the switch time is inaccessible, so we can't
- * do the adjustment and will end up with a wrong
- * runtime. A previous call with a different
- * curthread may have obtained a (right or wrong)
- * runtime that is in advance of ours. Just set a
- * flag to avoid warning about this known problem.
+ * Adjust for the current time slice. This is
+ * important since the adjustment is on the order
+ * of a time quantum, which is much greater than
+ * precision of binuptime().
*/
- problemcase = 1;
+ if (!bt_valid) {
+ binuptime(&bt);
+ bt_valid = 1;
+ }
+ bintime_add(&rt, &bt);
+ bintime_sub(&rt,
+ &pcpu_find(td->td_oncpu)->pc_switchtime);
}
}
@@ -751,8 +745,7 @@
ptu = p->p_uu + p->p_su + p->p_iu;
if (tu < ptu) {
- if (!problemcase)
- printf(
+ printf(
"calcru: runtime went backwards from %ju usec to %ju usec for pid %d (%s)\n",
- (uintmax_t)ptu, (uintmax_t)tu, p->p_pid, p->p_comm);
+ (uintmax_t)ptu, (uintmax_t)tu, p->p_pid, p->p_comm);
tu = ptu;
}
%%%
Bruce
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