* Question: Takes about 2s in sched_clock_init() when kernel boots
@ 2013-10-31 5:29 Younger Liu
2013-10-31 6:12 ` Xie XiuQi
0 siblings, 1 reply; 2+ messages in thread
From: Younger Liu @ 2013-10-31 5:29 UTC (permalink / raw)
To: kernel
Hi,
When I analyse boot time on ArmV7, I found that it takes
about 2s in sched_clock_init(), the log is as follow:
[ 0.000000] before:sched_clock_init.
[ 0.000000] start:sched_clock_init.
[ 2.100505] end :sched_clock_init.
[ 2.103983] before:calibrate_delay.
In my config, CONFIG_HAVE_UNSTABLE_SCHED_CLOCK does not config.
Are there any suggestions?
Younger
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Question: Takes about 2s in sched_clock_init() when kernel boots
2013-10-31 5:29 Question: Takes about 2s in sched_clock_init() when kernel boots Younger Liu
@ 2013-10-31 6:12 ` Xie XiuQi
0 siblings, 0 replies; 2+ messages in thread
From: Xie XiuQi @ 2013-10-31 6:12 UTC (permalink / raw)
To: Younger Liu; +Cc: kernel
On 2013/10/31 13:29, Younger Liu wrote:
> Hi,
> When I analyse boot time on ArmV7, I found that it takes
> about 2s in sched_clock_init(), the log is as follow:
> [ 0.000000] before:sched_clock_init.
> [ 0.000000] start:sched_clock_init.
> [ 2.100505] end :sched_clock_init.
> [ 2.103983] before:calibrate_delay.
>
> In my config, CONFIG_HAVE_UNSTABLE_SCHED_CLOCK does not config.
>
> Are there any suggestions?
see below:
u64 sched_clock_cpu(int cpu)
{
struct sched_clock_data *scd;
u64 clock;
WARN_ON_ONCE(!irqs_disabled());
if (sched_clock_stable)
return sched_clock();
if (unlikely(!sched_clock_running))
return 0ull;
scd = cpu_sdc(cpu);
[...]
Unless sched_clock_running is set, it'll return 0. So, the
printk() time stamp is 0 before sched_clock_init calling.
>
> Younger
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