On Tue, Jan 08, 2013 at 03:08:07AM +0100, Frederic Weisbecker wrote:
[ … ]
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index 8601f0d..dc6381d 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -70,6 +70,15 @@ config NO_HZ
> only trigger on an as-needed basis both when the system is
> busy and when the system is idle.
>
> +config NO_HZ_FULL
> + bool "Full tickless system"
I think you want to say here "Almost-completely tickless system".
"Almost" because of that one CPU outside of the range :-)
> + depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN &&
> RCU_NOCB_CPU && SMP
> + select CONTEXT_TRACKING_FORCE
> + help
> + Try to be tickless everywhere, not just in idle. (You need
> + to fill up the full_nohz_mask boot parameter).
> +
> +
> config HIGH_RES_TIMERS
> bool "High Resolution Timer Support"
> depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 314b9ee..494a2aa 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -142,6 +142,29 @@ static void tick_sched_handle(struct tick_sched *ts,
> struct pt_regs *regs)
> profile_tick(CPU_PROFILING);
> }
>
> +#ifdef CONFIG_NO_HZ_FULL
> +static cpumask_var_t full_nohz_mask;
> +bool have_full_nohz_mask;
> +
> +int tick_nohz_full_cpu(int cpu)
> +{
> + if (!have_full_nohz_mask)
> + return 0;
> +
> + return cpumask_test_cpu(cpu, full_nohz_mask);
> +}
> +
> +/* Parse the boot-time nohz CPU list from the kernel parameters. */
> +static int __init tick_nohz_full_setup(char *str)
> +{
> + alloc_bootmem_cpumask_var(&full_nohz_mask);
> + have_full_nohz_mask = true;
> + cpulist_parse(str, full_nohz_mask);
Don't you want to check retval of cpulist_parse first here before
assigning have_full_nohz_mask and allocating cpumask var?
We don't trust userspace, you know.
> + return 1;
> +}
> +__setup("full_nohz=", tick_nohz_full_setup);
I'd guess this kernel parameter needs to go into
Documentation/kernel-parameters.txt along with a referral to
Documentation/cputopology.txt which explains how to specify cpulists for
n00bs like me :-)
Thanks.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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