Messages in this thread |  | | Date | Thu, 31 Oct 2013 14:12:57 +0800 | From | Xie XiuQi <> | Subject | Re: Question: Takes about 2s in sched_clock_init() when kernel boots |
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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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > >
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