Has anyone successfully used perf within an ESX VM? dmesg shows a PMU is
discovered:
dmesg | grep -i performance
Performance Events: Nehalem/Corei7 events, Intel PMU driver.
yet data from it is nonsensical:
perf stat -v -- /tmp/a
task-clock-msecs: 20593318 20593318 20593318
context-switches: 2 20593318 20593318
CPU-migrations: 0 20593318 20593318
page-faults: 387 20593318 20593318
cycles: 10737418235 20593318 20593318
instructions: 10737418235 20593318 20593318
cache-references: 10737418235 20593318 20593318
cache-misses: 10737418235 20593318 20593318
Performance counter stats for '/tmp/a':
20.593318 task-clock-msecs # 0.988 CPUs
2 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
387 page-faults # 0.019 M/sec
10737418235 cycles # 521403.022 M/sec
10737418235 instructions # 1.000 IPC
10737418235 cache-references # 521403.022 M/sec
10737418235 cache-misses # 521403.022 M/sec
0.020837863 seconds time elapsed
David
/tmp/a -- a step above 'sleep 1'
#!/bin/sh
declare -i i=0;
declare -i sum=0;
while [ $i -lt 1000 ]
do
sum=$((sum + i))
i=$((i+1))
done
echo "sum $sum"
On Fri, May 27, 2011 at 01:33:54PM -0600, David Ahern wrote:
>
> Has anyone successfully used perf within an ESX VM? dmesg shows a PMU is
> discovered:
Don't know about ESX. But in general, getting this right requires
virtualizing PMU hardware (eg: save/restore PMU state on exit/entry
from the guest just the way the scheduler does for processes).
Also, the MSR read/writes to event-{select,count} registers must
be properly virtualized. Interrupt delivery (NMIs) is important
as well.
I suspect that MSR writes from the guest to the PMU related registers
are simply ignored in most virtual environments today.
-Arun