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profile thoughts and feedback
- From: Benjamin Kosnik <bkoz at redhat dot com>
- To: libstdc++ at gcc dot gnu dot org, rus at google dot com
- Date: Fri, 30 Oct 2009 11:13:10 -0700
- Subject: profile thoughts and feedback
Here are some collected notes based on two disjoint conversations about
the recently contributed profile mode, one with Paolo and one with
Silvius Rus.
1. Docs
- need news item for http://gcc.gnu.org/news.html
- need 4.5 release note changes item for
http://gcc.gnu.org/gcc-4.5/changes.html
- public link for CGO paper requested
Perflint: A Context Sensitive Performance Advisor for C++ Programs
http://www.computer.org/portal/web/csdl/doi/10.1109/CGO.2009.36
explore hosting this as part of
http://research.google.com/pubs/papers.html
2. Diagnostics
- under development are the following
vector_to_deque
list_to_forward_list
list_to_set
iterator*
- interest in these
string: c++2003 vs. c++200x
string vs. vector
__gnu_cxx::__versa_string policies,
__rc_string_base vs. __sso_string_base in various sizes (which?)
3. More accurate cost models
- trunk has constant defaults
- exploring a host-specific, generated cost model. Approach being
considered is to generate some emperical cost model by
synthetic runs measured on the host machine.
- outstanding questions
a. interface to performance counters uncertain
PAPI http://icl.cs.utk.edu/papi/
SystemTap http://sourceware.org/systemtap/
b. where to put the generation tools? This something kind of like
abi_check, in that it is a built executable that is then used as
part of testing/analysis. Something like scripts for .py files, but
for binaries? Host external to libstdc++?
c. how much of this is defaulted constants, how much algorithmic,
how much measured and stored in a persistent format? How is this
situation similar to FDO?
4. Branch development
- branch will continue to merge in all new changes
- checkpoint at the end of november to see where branch stands WRT
cost model development
-benjamin