Re: Dynamic Ticks/HZ

From: Davide Italiano <davide_at_freebsd.org>
Date: Mon, 5 Nov 2012 07:52:56 +0100
On Nov 4, 2012 10:40 PM, "Joe Holden" <lists_at_rewt.org.uk> wrote:
>
> Davide Italiano wrote:
>>
>> On Mon, Nov 5, 2012 at 7:12 AM, Joe Holden <lists_at_rewt.org.uk> wrote:
>>>
>>> Hi guys,
>>>
>>> Has some default changed between 9.1-RC2 and HEAD?
>>>
>>> On identical machines, one with 9.1-RC2 and one with HEAD from yesterday
>>> (GENERIC) I see the following in systat -v:
>>>
>>> 9.1:
>>> 65 cpu0:timer
>>> 10 cpu1:timer
>>>
>>> HEAD:
>>> 1127 cpu0:timer
>>> 22 cpu1:timer
>>>
>>> These are Supermicro i3 boxes and as far as I can see they have matching
>>> BIOS config.
>>>
>>> Thanks,
>>> J
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>>
>>
>> Which is your refresh rate for systat?
>> I generally measure sampling every one second (i.e. systat -vm 1).
>> Also, are you making your measurements when the system is idle?
>> In order to trace the source(s) of these interrupts you might consider
>> to collect data via KTR.
>>
>
> I'm also using a one second refresh rate, the system is entirely idle and
the interupt rate is almost entirely static at 1127, occasionally it will
drop to 1119.
>
> From what I understand the timer is hz/ticks which became dynamic in 9.0,
although that behaviour doesn't appear to be in HEAD anymore, at least on
this hardware.
>
> Thanks,
> J

It should be available, AFAIK. As I can see from your previous post you get
about 20 interrupts on cpu1. This number is about 1/100 of the value you
get on a !tickless kernel.
If you provide the required ktr infos, probably someone will take a look.
Received on Mon Nov 05 2012 - 05:52:57 UTC

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