Messages in this thread | | | Date | Sun, 6 Nov 2005 16:13:59 +0200 | From | erezz@techunix ... | Subject | CPU utilization and hyperthreading |
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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
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