High load event idl.

[Oliver Pinter]

http://oliverp.teteny.bme.hu/freebsd/ktr/

On 4/29/12, Alexander Motin <mav at freebsd.org> wrote:
> On 04/29/12 15:04, Oliver Pinter wrote:
>> Removing dummynet from kernel don't chanage anything, that is releated
>> to load average. The loadavg hold to 0.70 +/- 0.2. (single user : sh +
>> top)
>
> New ktr dump?
>
>> On 4/29/12, Alexander Motin<mav at freebsd.org>  wrote:
>>> On 04/29/12 09:09, Ian Smith wrote:
>>>> On Sun, 29 Apr 2012 08:17:38 +0300, Alexander Motin wrote:
>>>>    >   On 04/29/12 01:53, Oliver Pinter wrote:
>>>>    >   >   Attached the ktr file. This is on core2duo P9400 cpu (
>>>>    >   >   smbios.system.product="HP ProBook 5310m (WD792EA#ABU)" ).
>>>> The
>>>> workload
>>>>    >   >   is only a single user boost: sh + top running, but the load
>>>> average is
>>>>    >   >   near 0.5.
>>>>    >
>>>>    >   ktr shows no real load there. But it shows that you are using
>>>> dummynet, that
>>>>    >   schedules its runs on every hardclock tick. I believe that load
>>>> you
>>>> see is
>>>>    >   the result or synchronization between dummynet calls and loadvg
>>>> sampling,
>>>>    >   both of which called from hardclock. I think removing dummynet
>>>> from
>>>> equation,
>>>>    >   should hide this problem and also reduce you laptops power
>>>> consumption.
>>>>    >
>>>>    >   What's about fixing this, it is loadavg sampling algorithm that
>>>> should be
>>>>    >   changed. Fixing dummynet to not run on every hardclock tick
>>>> would
>>>> also be
>>>>    >   great.
>>>>
>>>> Wading in out of my depth, and copying Luigi in case he misses it ..
>>>> but
>>>> even back in the olden days when HZ defaulted to 100, one was advised
>>>> to
>>>> use HZ>= 1000 for smooth dummynet traffic shaping dispatch scheduling.
>>>>
>>>> I wonder, with the newer clocks and timers, whether there is another
>>>> clock that could be used for dummynet scheduling, that would not have
>>>> this effect (even if largely cosmetic?) on load average calculation?
>>>
>>> First of all, the easiest solution would be to make dummynet to schedule
>>> callout not automatically, but on first queued packet. I believe that in
>>> case of laptop the queue should be empty most of time and the callout
>>> calls are completely useless there. Luigi promised to look on this once.
>>>
>>> What's about better precision/removing synchronization -- there is
>>> starting GSoC project now (by davide@) to rewrite callout(9) subsystem
>>> to use better precision allowed by new timer drivers. While now it is
>>> possible to get raw access to additional timer hardware available on
>>> some systems, I don't think it is a good idea.
>
>
> --
> Alexander Motin
>