Trigger softirq less frequently
We trigger the softirq before this patch using offset of
sd->interval. However, if the queue is busy then it is sufficient
to schedule the softirq with sd->interval * busy_factor.
So we modify the calculation of the next time to balance by taking
the interval added to last_balance again. This is only the
right value if the idle/busy situation continues as is.
There are two potential trouble spots:
- If the queue was idle and now gets busy then we call rebalance
early. However, that is not a problem because we will then use
the longer interval for the next period.
- If the queue was busy and becomes idle then we potentially
wait too long before rebalancing. However, when the task
goes idle then idle_balance is called. We add another calculation
of the next balance time based on sd->interval in idle_balance
so that we will rebalance soon.
V2->V3:
- Calculate rebalance time based on current jiffies and not
based on the jiffies at the last time we load balanced.
We no longer rely on staggering and therefore we can
affort to do this now.
V3->V4:
- Use functions to do jiffy comparisons.
Signed-off-by: Christoph Lameter <[email protected]>
Index: linux-2.6.19-rc5-mm1/kernel/sched.c
===================================================================
--- linux-2.6.19-rc5-mm1.orig/kernel/sched.c 2006-11-13 18:11:07.034196836 -0600
+++ linux-2.6.19-rc5-mm1/kernel/sched.c 2006-11-13 19:04:40.316317645 -0600
@@ -2777,14 +2777,28 @@ out_balanced:
static void idle_balance(int this_cpu, struct rq *this_rq)
{
struct sched_domain *sd;
+ int pulled_task = 0;
+ unsigned long next_balance = jiffies + 60 * HZ;
for_each_domain(this_cpu, sd) {
if (sd->flags & SD_BALANCE_NEWIDLE) {
/* If we've pulled tasks over stop searching: */
- if (load_balance_newidle(this_cpu, this_rq, sd))
+ pulled_task = load_balance_newidle(this_cpu,
+ this_rq, sd);
+ if (time_after(next_balance,
+ sd->last_balance + sd->balance_interval))
+ next_balance = sd->last_balance
+ + sd->balance_interval;
+ if (pulled_task)
break;
}
}
+ if (!pulled_task)
+ /*
+ * We are going idle. next_balance may be set based on
+ * a busy processor. So reset next_balance.
+ */
+ this_rq->next_balance = next_balance;
}
/*
@@ -2907,7 +2921,7 @@ static void run_rebalance_domains(struct
*/
idle = NOT_IDLE;
}
- sd->last_balance += interval;
+ sd->last_balance = jiffies;
}
if (time_after(next_balance, sd->last_balance + interval))
next_balance = sd->last_balance + interval;
-
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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
