[SOLVED] oprofile isn't sampling LLC

oprofile isn't sampling LLC_MISSES cache events

I'm trying to use oprofile to record cache misses in a large realtime app:

$ sudo opcontrol --no-vmlinux --event=LLC_MISSES:100000 --session-dir=/var/tmp/oprofile -c=5 --start

But when I look at the reports, it doesn't mention the cache misses. It only samples CPU_CLK_UNHALTED:

$ sudo opreport -l --session-dir=/var/tmp/oprofile 

CPU: Intel Architectural Perfmon, speed 1596 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
samples  %        image name               app name                 symbol name
63243    92.2946  no-vmlinux               no-vmlinux               /no-vmlinux
564       0.8231  libc-2.13.so             libc-2.13.so             /lib32/libc-2.13.so
 (etc)

But --status claims that oprofile is sampling L2 misses:

$ sudo opcontrol --status

Daemon running: pid 3220
Event 0: LLC_MISSES:500000:65:1:1
Separate options: library
vmlinux file: none
Image filter: none
Call-graph depth: 5

What am I doing wrong? I can't get it to sample any of the other counters listed in ophelp either.

This is with oprofile 0.9.6 on Ubuntu, kernel version 2.6.38.

Solution

Turns out you need to actually kill and restart the oprofile daemon with

sudo opcontrol --stop
sudo opcontrol --reset
sudo opcontrol --shutdown
sudo opcontrol --start-daemon
sudo opcontrol --start

when changing sampled events. Simply stopping and starting the profile isn't enough. Not that this is documented anywhere.