On Wed, Apr 7, 2010 at 3:15 PM, Peter Zijlstra <pet...@infradead.org> wrote: > On Wed, 2010-04-07 at 14:45 +0200, Stephane Eranian wrote: >> LBR is configured by default to record ALL taken branches. On some >> processors, it is possible to filter the type of branches. This will >> be supported in a subsequent patch. >> >> On other processors, the sample type is allowed but will generate a >> sample where nr=0 as is the case with other sampling types. > > Right, so I already posted a patch like that: > http://lkml.org/lkml/2010/3/4/160 > > and the reason its not merged is because there is no perf use-case for > it. Ingo wants to avoid merging ABI bits for which there is no userspace > around. We already have a few such things and we find that its too easy > to regress on those part. > Then, why didn't you extend perf to leverage your patch?
I think that forcing all features to be included in perf in not a very attractive approach. It can't be the only approach. There are many usage models of PMU data. You want to encourage the development of as many tools and libraries as possible. It helps with validation too. There are bugs in your implementation which are not exposed simply because perf does not need the features. But that does not mean those features are not useful. To encourage developers, you need to build simple examples of how each feature can be used. You don't necessarily need a fully featured tool. This is what I am doing with libpfm4. People can learn from the examples and built their own custom tools and libraries. If I post a patch to enable LBR sampling, it is because I have a user level test program to validate it and demonstrate what you can get out. LBR data typically has lots of post-processing. It is best suited for offline processing. You could use perf to collect the data and dump a binary output file. I can take a look at that. I also assume that the same reason is holding up my randomization patch. yet I think this is an important feature. ------------------------------------------------------------------------------ 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
