Messages in this thread | | | Date | Mon, 11 Feb 2013 15:35:29 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 07/33] nohz: Basic full dynticks interface |
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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.
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