Hello,
The values in /proc/loadavgrt are sometimes the real load and sometimes
garbage. As you can see in th tests below, it occurs from in 2.6.21.5-rt20
to 2.6.23-rc2-rt2. The code for calc_load(), in kernel/timer.c has not
changed much in -rt patches.
[lclaudio@lab sandbox]$ ls /proc/loadavg*
/proc/loadavg /proc/loadavgrt
[lclaudio@lab sandbox]$ uname -a
Linux lab.casa 2.6.21-34.el5rt #1 SMP PREEMPT RT Thu Jul 12 15:26:48 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
[lclaudio@lab sandbox]$ cat /proc/loadavg*
4.57 4.90 4.16 3/146 23499
0.44 0.98 1.78 0/146 23499
...
[lclaudio@lab sandbox]$ cat /proc/loadavg*
4.65 4.80 4.75 5/144 20720
23896.04 -898421.23 383170.94 2/144 20720
[root@neverland ~]# uname -a
Linux neverland.casa 2.6.21.5-rt20 #2 SMP PREEMPT RT Fri Jul 1318:31:38 BRT 2007 i686 athlon i386 GNU/Linux
[root@neverland ~]# cat /proc/loadavg*
0.16 0.16 0.15 1/184 11240
344.65 0.38 311.71 0/184 11240
[williams@torg ~]$ uname -a
Linux torg 2.6.23-rc2-rt2 #14 SMP PREEMPT RT Tue Aug 7 20:07:31 CDT 2007 x86_64 x86_64 x86_64 GNU/Linux
[williams@torg ~]$ cat /proc/loadavg*
0.88 0.76 0.57 1/257 7267
122947.70 103790.53 -564712.87 0/257 7267
---------->
Fixes spurious system load spikes observed in /proc/loadavgrt, as described in:
Bug 253103: /proc/loadavgrt issues weird results
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=253103
Signed-off-by: Luis Claudio R. Goncalves <lclaudio@xxxxxxxx>
---
diff --git a/kernel/sched.c b/kernel/sched.c
index 811a502..c61609a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2520,6 +2520,13 @@ unsigned long rt_nr_uninterruptible(void)
for_each_online_cpu(i)
sum += cpu_rq(i)->rt_nr_uninterruptible;
+ /*
+ * Since we read the counters lockless, it might be slightly
+ * inaccurate. Do not allow it to go below zero though:
+ */
+ if (unlikely((long)sum < 0))
+ sum = 0;
+
return sum;
}
diff --git a/linux-2.6.21.x86_64/kernel/timer.c b/linux-2.6.21.x86_64_lc/kernel/timer.c
index 882ca9d..0e49bf6 100644
--- a/linux-2.6.21.x86_64/kernel/timer.c
+++ b/linux-2.6.21.x86_64_lc/kernel/timer.c
@@ -1432,23 +1432,25 @@ unsigned long avenrun_rt[3];
static inline void calc_load(unsigned long ticks)
{
unsigned long active_tasks; /* fixed-point */
+ unsigned long active_rt_tasks; /* fixed-point */
static int count = LOAD_FREQ;
count -= ticks;
if (unlikely(count < 0)) {
active_tasks = count_active_tasks();
+ active_rt_tasks = count_active_rt_tasks();
do {
CALC_LOAD(avenrun[0], EXP_1, active_tasks);
CALC_LOAD(avenrun[1], EXP_5, active_tasks);
CALC_LOAD(avenrun[2], EXP_15, active_tasks);
- count += LOAD_FREQ;
- } while (count < 0);
#ifdef CONFIG_PREEMPT_RT
- active_tasks = count_active_rt_tasks();
- CALC_LOAD(avenrun_rt[0], EXP_1, active_tasks);
- CALC_LOAD(avenrun_rt[1], EXP_5, active_tasks);
- CALC_LOAD(avenrun_rt[2], EXP_15, active_tasks);
+ CALC_LOAD(avenrun_rt[0], EXP_1, active_tasks);
+ CALC_LOAD(avenrun_rt[1], EXP_5, active_tasks);
+ CALC_LOAD(avenrun_rt[2], EXP_15, active_tasks);
#endif
+ count += LOAD_FREQ;
+
+ } while (count < 0);
}
}
-
--
[ Luis Claudio R. Goncalves lclaudio at uudg dot org ]
[ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9 2696 7203 D980 A448 C8F8 ]
[ Linux-HA Developer - LateNite Programmer - Gospel User - Bass Player ]
[ Fault Tolerance - Real-Time - Distributed Systems - IECLB - Is 40:31 ]
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