document -prof_pcs and provide support for profiling joint DR+client

[derekbruening]

From derek.br...@gmail.com on May 06, 2009 11:27:32

The older MIT releases documented -prof_pcs and provided other profiling
options. We took out the latter as they weren't worth the effort to support
and could be written as simple clients. It might be worth officially
documenting -prof_pcs, however, and provide support/tools for analyzing
performance of clients.

xref PR 225255: release PROFILE_LINKCOUNT build?
xref PR 225139: expose performance-affecting configuration runtime options

Original issue: http://code.google.com/p/dynamorio/issues/detail?id=140

[derekbruening]

From bruen...@google.com on September 28, 2011 08:16:33

Labels: GoodContrib

[derekbruening]

From bruen...@google.com on September 28, 2011 08:22:33

Owner: ---

[derekbruening]

From zhao...@google.com on May 03, 2013 11:59:57

we could also export API to update dcontext->whereami, so the client can have customized information of sampling distribution.

[byron-hawkins]

Two additional issues with profiling clients:

1. If the client acquires locks, the profiler will potentially deadlock (or hit rank-order asserts) because for interrupts occurring in client code, whereami will still (erroneously) be WHERE_FCACHE.
2. The profiler will crash on exit if samples are taken in client code, because (a) the profiler will label each client pc as WHERE_UNKNOWN (after failing to find it in the fcache), and (b) the profiler disassembles every pc labeled WHERE_UNKNOWN during the final report, which crashes because the client module has already been unloaded at that point.

[derekbruening]

Just to clarify, 1. above should say "occurring in client clean callees out of the code cache", not arbitrary client code.

[byron-hawkins]

The two client issues are fixed in 2675a1b. I'm leaving this issue open because the public documentation for -prof_pcs has still not been addressed.