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Description of problem: Starting the oprofile daemon fails, due to nmi_watchdog using counter 0 Version-Release number of selected component (if applicable): rpm -q oprofile oprofile-0.9.6-14.fc15.x86_64 How reproducible: Always on stock F15 (I think) Steps to Reproduce: 1. opcontrol --no-vmlinux --image=path/to/binary 2. opcontrol --start Actual results: Error: counter 0 not available nmi_watchdog using this resource ? Try: opcontrol --deinit echo 0 > /proc/sys/kernel/nmi_watchdog Expected results: oprofile daemon started Additional info: It seems inconvenient needing to do both, opcontrol --deinit echo 0 > /proc/sys/kernel/nmi_watchdog before the oprofile daemon actually starts.
The problem is due to changes in how Linux kernel's watchdog timer reserves the performance counter hardware. It use to be that the watchdog timer, perf, and systemtap each used a different software mechanism. The watchdog timer has been merged into the perf framework. The downside of this is perf takes all the performance hardware when any of the performance monitoring hardware is being used by perf. Thus, oprofile, gets no counters when the nmi_watchdog is active.
What would be the drawback of doing: opcontrol --deinit echo 0 > /proc/sys/kernel/nmi_watchdog before any profiling is done on F15? Or perhaps check if this perf. counter is used by something else, if so offer a better suggestion than just fail?
Severin, it might be best if we throw a dialogue saying that the user needs to do that. Will suggested on IRC that some sysadmins may want to keep the nmi watchdog on so it's probably best to not turn it off under the covers.
I'm running into this on F16 as well. It's fairly annoying that oprofile is unusable by default because somebody arbitrarily decided they could break it. I think the use of these hardware resources needs to be renegotiated.
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The problem persists in Fedora 18 Alpha. "Perf" should have an interface to [re-]negotiate the use of the 4 HPET timers, and oprofile should use it. -----syslog (/var/log/messages) kernel: [ 1.310896] HPET: 4 timers in total, 0 timers will be used for per-cpu timer kernel: [ 1.317809] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0 kernel: [ 1.323076] hpet0: 4 comparators, 64-bit 14.318180 MHz counter -----