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Diffstat (limited to 'doc/src/analyze/cpu-usage-analyzer.qdoc')
| -rw-r--r-- | doc/src/analyze/cpu-usage-analyzer.qdoc | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/doc/src/analyze/cpu-usage-analyzer.qdoc b/doc/src/analyze/cpu-usage-analyzer.qdoc index 432e9fb917d..095cc7fe4c8 100644 --- a/doc/src/analyze/cpu-usage-analyzer.qdoc +++ b/doc/src/analyze/cpu-usage-analyzer.qdoc @@ -271,9 +271,19 @@ \li Some versions of Perf will not start recording unless given a certain minimum sampling frequency. Try with a \uicontrol {Sampling Frequency} of 1000. - \li On some devices, Perf support is not very stable and the Linux - kernel may randomly fail to record data after some time. Reboot the - device and try again. + \li On some devices, for example Boundary Devices i.MX6 Boards, the + Perf support is not very stable and the Linux kernel may randomly + fail to record data after some time. Perf can use different types + of events to trigger samples. You can get a list of available event + types by running \c {perf list} on the device and add + \c {-e <event type>} to the \uicontrol {Additional arguments} field + to change the event type to be used. The choice of event type + affects the performance and stability of the sampling. + \c {-e cpu-clock} is a safe but relatively slow option as it + does not use the hardware performance counters, but drives the + sampling from software. After the sampling has failed, reboot the + device. The kernel may have disabled important parts of the + performance counters system. \endlist Output from the helper program that processes the data is displayed in the |