Hi Vincent,
On 19/11/12 09:20, Vincent Guittot wrote:
Hi,
On 16 November 2012 19:32, Liviu Dudau <liviu.du...@arm.com> wrote:
From: Morten Rasmussen <morten.rasmus...@arm.com>
Re-enable SD_SHARE_POWERLINE to reflect the power domains of TC2.
---
arch/arm/kernel/topology.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 317dac6..4d34e0e 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -228,7 +228,7 @@ struct cputopo_arm cpu_topology[NR_CPUS];
int arch_sd_share_power_line(void)
{
- return 0*SD_SHARE_POWERLINE;
+ return 1*SD_SHARE_POWERLINE;
I'm not sure to catch your goal. With this modification, the power
line (or power domain) is shared at all level which should disable the
packing mechanism. But in a previous patch you fix the update packing
loop so I assume that you want to use it. Which kind of configuration
you would like to have among the proposal below ?
cpu : CPU0 | CPU1 | CPU2 | CPU3 | CPU4
buddy conf 1 : CPU2 | CPU0 | CPU2 | CPU2 | CPU2
buddy conf 2 : CPU2 | CPU2 | CPU2 | CPU2 | CPU2
buddy conf 3 : -1 | -1 | -1 | -1 | -1
When we look at the git://git.linaro.org/arm/big.LITTLE/mp.git
big-LITTLE-MP-master-v12, we can see that you have defined a custom
sched_domain which hasn't been updated with SD_SHARE_POWERLINE flag so
the flag is cleared at CPU level. Based on this, I would say that you
want buddy conf 2 ? but I would say that buddy conf 1 should give
better result. Have you tried both ?
My goal with this fix is to set up the SD_SHARE_POWERLINE flags as they
really are on TC2. It could have been done more elegantly. Since the HMP
patches overrides the sched_domain flags at CPU level the
SD_SHARE_POWERLINE is not being set by arch_sd_share_power_line(). With
this fix we will get SD_SHARE_POWERLINE at MC level and no
SD_SHARE_POWERLINE at CPU level, which I believe is the correct set up
for TC2.
For the buddy configuration the goal is to get configuration 1 in your
list above. You should get that when using the other patch to fix the
buddy selection algorithm.
I'm not sure if conf 1 or 2 is best. I think it depends on the
power/performance trade-off of the specific platform. conf 1 may lead to
CPU1->CPU0->CPU2 migrations which may be undesirable. If your cpus are
very leaky it might make sense to not do packing at all inside a high
performance cluster and always do packing directly on a another low
power cluster like conf 2. I think this needs further investigation.
I have only tested with conf 1 on TC2.
Regards,
Morten
Regards,
Vincent
}
const struct cpumask *cpu_coregroup_mask(int cpu)
--
1.7.9.5
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