ntime
=====

Non-existent low-level performance counter monitoring library

I'm interested in creating a Linux library or kernel module that allows easy access to all of the performance counters supported by modern processors.  While designed to work across a number of processors, programs using it will not be 'portable' in the usual sense.  

The approach for each processor will take advantage of all the monitors that processor has to offer, rather than reducing to a common set shared by all. 
In particular, modern Intel processors offer a large number of 'uncore' performance monitors for memory access and other non-core-specific activities.  

I'd like to end up with a simple and transparent system instead of one that does everything.  I'd like it to have a few layers between it and the processor as possible, so that the AMD/Intel Architecture Guides can be used as documentation.  


Other similar tools that actually exist:

Linux perf:  https://github.com/torvalds/linux/tree/master/tools/perf
Difficult to use beyond a common subset of monitors.

pmu-tools: https://github.com/andikleen/pmu-tools
Intel specific extensions to the perf tools.  

likwid: https://code.google.com/p/likwid/
Aproach most similar to what I'm considering, best uncore support.

PAPI: http://icl.cs.utk.edu/papi/
Gigantic and complex.  I've never figured out where to start.

perfmon2/libpfm4: http://perfmon2.sourceforge.net/
Changed over time.  Now a helper front end to perf_events?

perfctr: http://user.it.uu.se/~mikpe/linux/perfctr/current/
Abandoned?

LiMiT: http://castl.cs.columbia.edu/limit/
Low overhead direct reads by Kernel patches

Papers: 

http://web.eece.maine.edu/~vweaver/projects/perf_events/overhead/fastpath2013_perfevents.pdf
Great overview as of 2013 of what's out there and how it came to be.

http://web3.cs.columbia.edu/~simha/preprint_isca11.pdf
2011 Summary, and reasons for wanting low-overhead measurements for LiMiT.