From: Milton Miller <miltonm@bga•com>
To: "Rune Torgersen" <runet@innovsys•com>
Cc: linuxppc-dev@ozlabs•org, Arnd Bergmann <arnd@arndb•de>
Subject: Re: 82xx performance
Date: Fri, 25 Jul 2008 22:47:36 -0500 [thread overview]
Message-ID: <52cfb363300164e2d5d566ac635e9d20@bga.com> (raw)
In-Reply-To: <DCEAAC0833DD314AB0B58112AD99B93B04BC5B2A@ismail.innsys.innovsys.com>
On Jul 25, 2008, at 3:41 PM, Rune Torgersen wrote:
>> From: Arnd Bergmann [mailto:arnd@arndb•de]
>> On Thursday 17 July 2008, Rune Torgersen wrote:
>>> Arnd Bergmann wrote:
>>>> So again, nothing conclusive. I'm running out of ideas.
>>>
>>> Is the syscall path different or the same on ppc and powerpc?
>>> Any differences in the task switching, irq handling or page fault
>>> handling?
>>>
>>
>> It's all different in suble ways, but those changes should only
>> show up in the system time accounting, not user time accounting.
>
> I've been running the workload this board will see. On a 2.6.18 kernel
> %idle is ~50% and %wa (waiting for IO) is less than 1% most of the
> time.
> On 2.6.25, the idle% is lower (by about 10-15%) and the %wa is
> consistently hovering around 20-30% sometimes spiking to 100%.
>
> The workload involves quite a bit of socket IO (TCP, UDP, Unix Sockets
> and TIPC) and disk IO.
> Any easy way of finding what is causing the wait for IO?
>
> (Ive been trying to get lttng to work, but not any good results so
> far).
In both idle and wait, the cpu is in the idle loop waiting for something
to do. The difference is that a cpu is considered in disk wait if the
there is a task in uninterruptible sleep that is not being counted as
waiting on another cpu.
With a significant change in wait time, I would suggest restating the
current observations to the linux-mm community, probably with a cc
to linux-kernel.
Be sure to state what you have done to equalize the comparison (eg
highmen, ram size left, etc).
There may be some tunables that could adjust the behavior.
milton
next prev parent reply other threads:[~2008-07-26 3:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-14 16:34 82xx performance Rune Torgersen
2008-07-14 20:44 ` Arnd Bergmann
2008-07-15 14:16 ` Rune Torgersen
2008-07-15 18:25 ` Rune Torgersen
2008-07-15 19:50 ` Arnd Bergmann
2008-07-16 21:08 ` Rune Torgersen
2008-07-16 21:45 ` Arnd Bergmann
2008-07-16 21:53 ` Rune Torgersen
2008-07-16 22:32 ` Arnd Bergmann
2008-07-17 15:12 ` Rune Torgersen
2008-07-17 15:47 ` Arnd Bergmann
2008-07-17 15:52 ` Rune Torgersen
2008-07-17 18:24 ` Rune Torgersen
2008-07-17 19:43 ` Arnd Bergmann
2008-07-17 19:54 ` Rune Torgersen
2008-07-17 21:32 ` Arnd Bergmann
2008-07-25 20:41 ` Rune Torgersen
2008-07-26 3:47 ` Milton Miller [this message]
2008-07-15 15:57 ` Milton Miller
2008-07-15 18:12 ` Rune Torgersen
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