On Thu, Mar 4, 2010 at 3:32 AM, Ingo Molnar <mi...@elte.hu> wrote: > > * eran...@google.com <eran...@google.com> wrote: > >> This patch adds support for randomizing the sampling period. Randomization >> is very useful to mitigate the bias that exists with sampling. The random >> number generator does not need to be sophisticated. This patch uses the >> builtin random32() generator. > >> + if (width > 63 || attr->freq) >> + return -EINVAL; > > Why not for freq counters? Those are semi-randomized already, but it might > make sense to make them 'more' randomized in special circumstances. That would > also allow us to enable the randomization in perf top and perf record, by > default. > What's the goal of freq? Achieve and maintain the target interrupt/rate. In doing so, it has to adjust the period (not randomly).
Randomization may prevent achieving the rate, or it may slow it down. What's the value add of that? > Without that we'd have no immediate usecase and no way to ensure that this > code works as intended. > Why? With perf you also have fixed sampling period (-c option), you simply need to express the fact you want it randomized. > Thanks, > > Ingo > -- Stephane Eranian | EMEA Software Engineering Google France | 38 avenue de l'Opéra | 75002 Paris Tel : +33 (0) 1 42 68 53 00 This email may be confidential or privileged. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it went to the wrong person. Thanks ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
