From: Michael Neuling <mikey@neuling.org>
To: Peter Zijlstra <peterz@infradead.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@ozlabs.org, Ingo Molnar <mingo@elte.hu>,
Gautham R Shenoy <ego@in.ibm.com>,
linux-kernel@vger.kernel.org,
Suresh Siddha <suresh.b.siddha@intel.com>
Subject: [PATCH 1/5] sched: fix capacity calculations for SMT4
Date: Fri, 09 Apr 2010 16:21:18 +1000 [thread overview]
Message-ID: <20100409062118.D4096CBB6C@localhost.localdomain> (raw)
In-Reply-To: <1270794078.794237.347827867455.qpush@pale>
When calculating capacity we use the following calculation:
capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
In SMT2, power will be 1178/2 (provided we are not scaling power with
freq say) and SCHED_LOAD_SCALE will be 1024, resulting in capacity
being 1.
With SMT4 however, power will be 1178/4, hence capacity will end up as
0.
Fix this by ensuring capacity is always at least 1 after this
calculation.
Signed-off-by: Michael Neuling <mikey@neuling.org>
---
I'm not sure this is the correct fix but this works for me.
Original post here:
http://lkml.org/lkml/2010/3/30/884
---
kernel/sched_fair.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
Index: linux-2.6-ozlabs/kernel/sched_fair.c
===================================================================
--- linux-2.6-ozlabs.orig/kernel/sched_fair.c
+++ linux-2.6-ozlabs/kernel/sched_fair.c
@@ -1482,6 +1482,7 @@ static int select_task_rq_fair(struct ta
}
capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+ capacity = max(capacity, 1UL);
if (tmp->flags & SD_POWERSAVINGS_BALANCE)
nr_running /= 2;
@@ -2488,6 +2489,7 @@ static inline void update_sg_lb_stats(st
sgs->group_capacity =
DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
+ sgs->group_capacity = max(sgs->group_capacity, 1UL);
}
/**
@@ -2795,9 +2797,11 @@ find_busiest_queue(struct sched_group *g
for_each_cpu(i, sched_group_cpus(group)) {
unsigned long power = power_of(i);
- unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+ unsigned long capacity;
unsigned long wl;
+ capacity = max(DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE), 1UL);
+
if (!cpumask_test_cpu(i, cpus))
continue;
next prev parent reply other threads:[~2010-04-09 6:21 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-09 6:21 [PATCH 0/5] sched: asymmetrical packing for POWER7 SMT4 Michael Neuling
2010-04-09 6:21 ` [PATCH 2/5] sched: add asymmetric packing option for sibling domain Michael Neuling
2010-04-13 12:29 ` Peter Zijlstra
2010-04-14 6:09 ` Michael Neuling
2010-04-09 6:21 ` Michael Neuling [this message]
2010-04-13 12:29 ` [PATCH 1/5] sched: fix capacity calculations for SMT4 Peter Zijlstra
2010-04-14 4:28 ` Michael Neuling
2010-04-16 13:58 ` Peter Zijlstra
2010-04-18 21:34 ` Michael Neuling
2010-04-19 14:49 ` Peter Zijlstra
2010-04-19 20:45 ` Michael Neuling
2010-04-29 6:55 ` Michael Neuling
2010-05-31 8:33 ` Peter Zijlstra
2010-06-01 22:52 ` Vaidyanathan Srinivasan
2010-06-03 8:56 ` Peter Zijlstra
2010-06-07 15:06 ` Srivatsa Vaddagiri
2010-04-09 6:21 ` [PATCH 4/5] sched: Mark the balance type for use in need_active_balance() Michael Neuling
2010-04-13 12:29 ` Peter Zijlstra
2010-04-15 4:15 ` Michael Neuling
2010-04-09 6:21 ` [PATCH 3/5] powerpc: enabled asymmetric SMT scheduling on POWER7 Michael Neuling
2010-04-09 6:48 ` Michael Neuling
2010-04-09 6:21 ` [PATCH 5/5] sched: make fix_small_imbalance work with asymmetric packing Michael Neuling
2010-04-13 12:29 ` Peter Zijlstra
2010-04-14 1:31 ` Suresh Siddha
2010-04-15 5:06 ` Michael Neuling
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