From 8e957f09c7bd4a6456881af73ad48b2b8eb1f7ee Mon Sep 17 00:00:00 2001 From: Ulf Hermann Date: Thu, 16 Apr 2015 15:17:17 +0200 Subject: [PATCH] Doc: Improve CPU Usage Analyzer documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add sections about extra command line options and troubleshooting. Change-Id: I2ecd7b32a211321bcf9c31ee65f92386b70958db Reviewed-by: Kari Hautamäki Reviewed-by: Joerg Bornemann --- doc/src/analyze/cpu-usage-analyzer.qdoc | 30 +++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/doc/src/analyze/cpu-usage-analyzer.qdoc b/doc/src/analyze/cpu-usage-analyzer.qdoc index e3eb74cdfdc..432e9fb917d 100644 --- a/doc/src/analyze/cpu-usage-analyzer.qdoc +++ b/doc/src/analyze/cpu-usage-analyzer.qdoc @@ -132,6 +132,14 @@ data, and the processing delay may grow excessively. You should then lower the \uicontrol {Sampling frequency} or the \uicontrol {Stack snapshot size}. + \section2 Adding Command Line Options For Perf + + You can specify additional command line options to be passed to Perf when + recording data in the \uicontrol {Additional arguments} field. You may want + to specify \c{--no-delay} or \c{--no-buffering} to reduce the processing delay. + However, those options are not supported by all versions of Perf and Perf may + not start if an unsupported option is given. + \section1 Analyzing Collected Data The \uicontrol Timeline view displays a graphical representation of CPU @@ -248,4 +256,26 @@ back its own data in a sensible way by checking the output of \c {perf report} or \c {perf script} in the recorded Perf data files. + \section1 Troubleshooting + + The CPU Usage Analyzer might fail to record data for the following reasons: + + \list 1 + \li The connection between the target device and the host may not be + fast enough to transfer the data produced by Perf. Try lowering + the \uicontrol {Stack snapshot size} or + \uicontrol {Sampling Frequency} settings. + \li Perf may be buffering the data forever, never sending it. Add + \c {--no-delay} or \c {--no-buffering} to the + \uicontrol {Additional arguments} field. + \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. + \endlist + + Output from the helper program that processes the data is displayed in the + \uicontrol {General Messages} output pane. */