Hi,
I'm using a 2.6.4-52 (Suse 9.1 pro distribution) kernel on a 3.2 dual
XEON machine (with hyperthreading).
I'm trying to analyze the performance of a kernel module that contains
4 kernel threads (3 of them are more active). Also, some of the work is
done in a tasklet. The CPU load (as shown in vmstat) doesn't reach more
than 50%. When trying to artificially stress the system with some
useless loops, the CPU load reaches 65% (but I cannot reach 100%). Also, the
interrupts count in vmstat is around 20000 (1000 when idle).
My questions are:
1. Why can't I reach 100%?
2. I guess that since I have 4 virtual CPUs (as shown in /proc/cpuinfo), not all
of them are stressed. Is there a way to see the CPU utilization for each CPU
(vmstat doesn't allow that)?
3. When I load a module with a kernel thread that runs an infinite loop, I get
25% CPU utilization (50% if I run 2 threads). Is it because I'm using 100% of a
single CPU (out of 4)?
4. How is the time spent in interrupt context estimated? Is it possible to view
it somehow?
Thanks
Erez
On Sunday 06 November 2005 16:13, [email protected] wrote:
> Hi,
>
> I'm using a 2.6.4-52 (Suse 9.1 pro distribution) kernel on a 3.2 dual
> XEON machine (with hyperthreading).
>
> I'm trying to analyze the performance of a kernel module that contains
> 4 kernel threads (3 of them are more active). Also, some of the work is
> done in a tasklet. The CPU load (as shown in vmstat) doesn't reach more
> than 50%. When trying to artificially stress the system with some
> useless loops, the CPU load reaches 65% (but I cannot reach 100%). Also, the
> interrupts count in vmstat is around 20000 (1000 when idle).
>
> My questions are:
> 1. Why can't I reach 100%?
You can.
# while true; do true; done &
# while true; do true; done &
# while true; do true; done &
# while true; do true; done &
> 2. I guess that since I have 4 virtual CPUs (as shown in /proc/cpuinfo), not all
> of them are stressed. Is there a way to see the CPU utilization for each CPU
> (vmstat doesn't allow that)?
top
> 3. When I load a module with a kernel thread that runs an infinite loop, I get
> 25% CPU utilization (50% if I run 2 threads). Is it because I'm using 100% of a
> single CPU (out of 4)?
> 4. How is the time spent in interrupt context estimated? Is it possible to view
> it somehow?
--
vda