Whenever jiffies is started at a multiple of 5*HZ or wraps, calc_load is
run exactly on the second which is when tasks using round_jiffies will
be scheduled to run. This has a bad effect on the load average, making
it tend towards 1.00 if a task happens to run every time the load is
being calculated.
This changes calc_load so that it updates load half a second after any
tasks scheduled using round_jiffies.
Signed-off-by: Simon Arlott <[EMAIL PROTECTED]>
Cc: Andrew Morton <[EMAIL PROTECTED]>
Cc: Arjan van de Ven <[EMAIL PROTECTED]>
---
This version starts count off at 0, since LOAD_FREQ + HZ/2 is no better
than LOAD_FREQ. The previous version is actually wrong, rounding count to
a negative value will only happen when getting calc_load running at the
right time related to jiffies, it won't be negative running normally -
even with NO_HZ.
kernel/timer.c | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c
index 6663a87..4abead0 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1226,17 +1226,19 @@ EXPORT_SYMBOL(avenrun);
static inline void calc_load(unsigned long ticks)
{
unsigned long active_tasks; /* fixed-point */
- static int count = LOAD_FREQ;
+ static int count = 0;
count -= ticks;
- if (unlikely(count < 0)) {
+ if (unlikely(count <= 0)) {
active_tasks = count_active_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);
+ } while (count <= 0);
+
+ count = round_jiffies_relative(count + HZ/2) - HZ/2;
}
}
--
1.5.0.1
--
Simon Arlott
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
