The patch titled
sched: call tasklet less frequently
has been added to the -mm tree. Its filename is
sched-call-tasklet-less-frequently.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: sched: call tasklet less frequently
From: Christoph Lameter <clameter@xxxxxxx>
We schedule the tasklet before this patch always with the value in
sd->interval. However, if the queue is busy then it is sufficient to schedule
the tasklet 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.
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: "Siddha, Suresh B" <suresh.b.siddha@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/sched.c | 24 ++++++++++++++++++++++--
1 files changed, 22 insertions(+), 2 deletions(-)
diff -puN kernel/sched.c~sched-call-tasklet-less-frequently kernel/sched.c
--- a/kernel/sched.c~sched-call-tasklet-less-frequently
+++ a/kernel/sched.c
@@ -2757,14 +2757,26 @@ 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);
+ next_balance = min(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;
}
/*
@@ -2889,8 +2901,16 @@ static void rebalance_domains(unsigned l
}
sd->last_balance += interval;
}
+ /*
+ * Calculate the next balancing point assuming that
+ * the idle state does not change. If we are idle and then
+ * start running a process then this will be recalculated.
+ * If we are running a process and then become idle
+ * then idle_balance will reset next_balance so that we
+ * rebalance earlier.
+ */
next_balance = min(next_balance,
- sd->last_balance + sd->balance_interval);
+ sd->last_balance + interval);
}
this_rq->next_balance = next_balance;
}
_
Patches currently in -mm which might be from clameter@xxxxxxx are
create-compat_sys_migrate_pages.patch
wire-up-sys_migrate_pages.patch
memory-page-alloc-minor-cleanups.patch
memory-page-alloc-minor-cleanups-fix.patch
get-rid-of-zone_table.patch
deal-with-cases-of-zone_dma-meaning-the-first-zone.patch
get-rid-of-zone_table-fix-3.patch
introduce-config_zone_dma.patch
optional-zone_dma-in-the-vm.patch
optional-zone_dma-in-the-vm-no-gfp_dma-check-in-the-slab-if-no-config_zone_dma-is-set.patch
optional-zone_dma-in-the-vm-no-gfp_dma-check-in-the-slab-if-no-config_zone_dma-is-set-reduce-config_zone_dma-ifdefs.patch
optional-zone_dma-for-ia64.patch
remove-zone_dma-remains-from-parisc.patch
remove-zone_dma-remains-from-sh-sh64.patch
set-config_zone_dma-for-arches-with-generic_isa_dma.patch
zoneid-fix-up-calculations-for-zoneid_pgshift.patch
radix-tree-rcu-lockless-readside.patch
sched-avoid-taking-rq-lock-in-wake_priority_sleeper.patch
sched-disable-interrupts-for-locking-in-load_balance.patch
sched-extract-load-calculation-from-rebalance_tick.patch
sched-stagger-load-balancing-in-build_sched_domains.patch
sched-move-idle-stat-calculation-into-rebalance_tick.patch
sched-use-tasklet-to-call-balancing.patch
sched-call-tasklet-less-frequently.patch
zvc-support-nr_slab_reclaimable--nr_slab_unreclaimable-swap_prefetch.patch
reduce-max_nr_zones-swap_prefetch-remove-incorrect-use-of-zone_highmem.patch
numa-add-zone_to_nid-function-swap_prefetch.patch
readahead-state-based-method-aging-accounting.patch
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