On Jul 25, 2008, at 3:41 PM, Rune Torgersen wrote:
From: Arnd Bergmann [mailto:[EMAIL PROTECTED]
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
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