答复: a bug on NO_HZ_FULL_ALL
Alex Shi
alex.shi at linaro.org
Mon Nov 18 22:15:12 EST 2013
On 11/19/2013 11:10 AM, Sunshaojie wrote:
> Hi Alex
>
> I tested it on kernel V3.10 and on 32bits ARM system.
> Where did you see this option opened only for 64bits?
>
kernel/time/Kconfig:
config NO_HZ_FULL
bool "Full dynticks system (tickless)"
# NO_HZ_COMMON dependency
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
# We need at least one periodic CPU for timekeeping
depends on SMP
# RCU_USER_QS dependency
depends on HAVE_CONTEXT_TRACKING
# VIRT_CPU_ACCOUNTING_GEN dependency
depends on 64BIT <=======
select NO_HZ_COMMON
select RCU_USER_QS
select RCU_NOCB_CPU
select VIRT_CPU_ACCOUNTING_GEN
select IRQ_WORK
>
> -----邮件原件-----
> 发件人: Alex Shi [mailto:alex.shi at linaro.org]
> 发送时间: 2013年11月19日 11:03
> 收件人: Shaojie Sun; viresh kumar
> 抄送: Vincent Guittot; Fathi Boudra; Guodong Xu; Amit Kucheria; Chris Redpath; Linaro Kernel; LAK; Frédéric Weisbecker; Kevin Hilman; Sunshaojie
> 主题: Re: a bug on NO_HZ_FULL_ALL
>
> On 11/14/2013 05:54 PM, Shaojie Sun wrote:
>> No, I think it is a bug.
>>
>> Because I tested the option with NO_HZ_FULL and without
>> NO_HZ_FULL_ALL. It had only little interruptes on CPU0 twd.
>> With same code, I added NO_HZ_FULL_ALL option. It had too many
>> interruptes on CPU0 twd.
>>
>> So the sumbitter just didn't test twd interrupts, when he expanded
>> NO_HZ_FULL option to all cpu.
>>
>> On Thu, Nov 14, 2013 at 4:09 PM, viresh kumar <viresh.kumar at linaro.org> wrote:
>>> On Thursday 14 November 2013 01:35 PM, Vincent Guittot wrote:
>>>> AFAICT, It's a none issue. In full nohz, a timer fires periodically
>>>> (around 4sec period on ARM IIRC) on one cpu (cpu0).
>>>
>>> Timer should always be running on CPU0, its out of nohz-full domain.
>>> Its cpu 1, where it will fire after long delays..
>>>
>>>
>>> https://wiki.linaro.org/WorkingGroups/PowerManagement/Doc/AdaptiveTic
>>> kless
>
>
> Shaojie,
> which kernel version has this bug?
> I just find only the v3.13 kernel has opened the NO_HZ_FULL for 32 bit kernel. and my testing base it.
>
> but for lsk, it is 3.10 kernel, so unless you are using 64bit kernel to do testing, is it right?
>
> --
> Thanks
> Alex
>
--
Thanks
Alex
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