build/docs/pgo.rst@6474c204b198 (annotated)
build/docs/pgo.rst
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | .. _pgo: |
| michael@0 | 2 | |
| michael@0 | 3 | =========================== |
| michael@0 | 4 | Profile Guided Optimization |
| michael@0 | 5 | =========================== |
| michael@0 | 6 | |
| michael@0 | 7 | :abbr:`PGO (Profile Guided Optimization)` is the process of adding |
| michael@0 | 8 | probes to a compiled binary, running said binary, then using the |
| michael@0 | 9 | run-time information to *recompile* the binary to (hopefully) make it |
| michael@0 | 10 | faster. |
| michael@0 | 11 | |
| michael@0 | 12 | How PGO Builds Work |
| michael@0 | 13 | =================== |
| michael@0 | 14 | |
| michael@0 | 15 | The supported interface for invoking a PGO build is to evaluate the |
| michael@0 | 16 | *build* target of client.mk with *MOZ_PGO* defined. e.g.:: |
| michael@0 | 17 | |
| michael@0 | 18 | $ make -f client.mk MOZ_PGO=1 |
| michael@0 | 19 | |
| michael@0 | 20 | This is equivalent to:: |
| michael@0 | 21 | |
| michael@0 | 22 | $ make -f client.mk profiledbuild |
| michael@0 | 23 | |
| michael@0 | 24 | Which is roughly equivalent to: |
| michael@0 | 25 | |
| michael@0 | 26 | #. Perform a build with *MOZ_PROFILE_GENERATE=1* and *MOZ_PGO_INSTRUMENTED=1* |
| michael@0 | 27 | #. Package with *MOZ_PGO_INSTRUMENTED=1* |
| michael@0 | 28 | #. Performing a run of the instrumented binaries |
| michael@0 | 29 | #. $ make maybe_clobber_profiledbuild |
| michael@0 | 30 | #. Perform a build with *MOZ_PROFILE_USE=1* |
| michael@0 | 31 | |
| michael@0 | 32 | Differences between toolchains |
| michael@0 | 33 | ============================== |
| michael@0 | 34 | |
| michael@0 | 35 | There are some implementation differences depending on the compiler |
| michael@0 | 36 | toolchain being used. |
| michael@0 | 37 | |
| michael@0 | 38 | The *maybe_clobber_profiledbuild* step gets its name because of a |
| michael@0 | 39 | difference. On Windows, this step merely moves some *.pgc* files around. |
| michael@0 | 40 | Using GCC or Clang, it is equivalent to a *make clean*. |
