Messages in this thread |  | | | Date | Fri, 14 Sep 2012 07:43:44 +0200 | | From | Ingo Molnar <> | | Subject | Re: [PATCH 3/3 v2] perf tool: give user better message if precise is not supported |
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* David Ahern <dsahern@gmail.com> wrote:
> Platforms (e.g., VM's) without support for precise mode get a confusing > error message. e.g., > $ perf record -e cycles:p -a -- sleep 1 > > Error: sys_perf_event_open() syscall returned with 95 (Operation not > supported). /bin/dmesg may provide additional information. > > No hardware sampling interrupt available. No APIC? If so then you can > boot the kernel with the "lapic" boot parameter to force-enable it. > sleep: Terminated > > which is not clear that precise mode might be the root problem. With this > patch: > > $ perf record -e cycles:p -fo /tmp/perf.data -- sleep 1 > Error: > 'precise' request may not be supported. Try removing 'p' modifier > sleep: Terminated > > v2: softened message to 'may not be' supported per Robert's suggestion
Well, either it's supported on this machine or it's not - why does the text have to be so unsure about it?
We use computers to increase determinism, not to insert extra uncertainty! ;-)
Thanks,
Ingo
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