This patch properly synchronizes all the global state in platform*.cpp, which
gets us a long way towards implementing bug 1330184.
- Most of the global state goes in a new class, ProfilerState, with a single
instance, gPS. All accesses to gPS are protected by gPSMutex. All functions
that access ProfilerState require a token proving that gPS is locked; this
makes things much clearer.
gRegisteredThreadsMutex is removed because it is subsumed by gPSMutex.
- gVerbosity, however, does not go in ProfilerState. It stays separate, and
gains its own mutex, gVerbosityMutex.
Also, the tracking of the current profiler state is streamlined. Previously it
was tracked via:
- stack_key_initialized, gInitCount, gSampler, gIsProfiling, gIsActive, and
gIsPaused.
Now it is tracked via:
- gPS, gPS->sActivity, and gPS->mIsPaused.
This means that the Sampler class is no longer necessary, and the patch removes
it.
Other changes of note made by the patch are as follows.
- It removes ThreadInfo::{mMutex,GetMutex}. This mutex was only used in two
places, and both these are now protected by gPSMutex.
- It tweaks the LOG calls. All the main functions (init(), shutdown(), start(),
stop()) now do consistent BEGIN/END logging, and a couple of other low-value
incidental LOG calls have been removed.
- It adds a lot of release assertions requiring that gPS be initialized (e.g.
profiler_init() has been called but profiler_shutdown() has not).
- It uses alphabetical order for everything involving profiler feature names.
- It removes Platform{Start,Stop}() and SamplerThread::{Start,Stop}Sampler().
These are no longer necessary now that SamplerThread::sInstance has been
replaced with ProfilerState::mSamplerThread which allows more direct access
to the current SamplerThread instance.
- It removes PseudoStack::mPrivacyMode. This was derived from the "privacy"
feature, and we now use gPS->mFeaturePrivacy directly, which is simpler.
It also replaces profiler_in_privacy_mode() with
profiler_is_active_and_not_in_privacy_mode(), which avoids an unnecessary
lock/unlock of gPSMutex on a moderately hot path.
Finally, the new code does more locking than the old one. A number of operation
The following operations now lock a mutex when they previously didn't; the
following are ones that are significant, according to some ad hoc profiling.
- profiler_tracing()
- profiler_is_active()
- profiler_is_active_and_not_in_privacy_mode()
- profiler_add_marker()
- profiler_feature_active()
- SamplerThread::Run() [when the profiler is paused]
All up this roughly doubles the amount of mutex locking done by the profiler.
It's probably possible to avoid this increase by allowing careful unlocked
access to three of the fields in ProfilerState (mActivityGeneration,
mFeaturePrivacy, mStartTime), but this should only be done as a follow-up if
the extra locking is found to be a problem.
--HG--
extra : rebase_source : c2e41231f131b3e9ccd23ddf43626b54ccc77b7b
They duplicate the equivalent SPS_* macros. (The SPS_* macros have already
crept into use in some places within LUL.)
--HG--
extra : rebase_source : 65ed6e6e147189814511b0ca38342fec118478b9
It's fairly straightforward, and measures the important parts of:
- Sampler, PseudoStack, ProfileBuffer, ThreadInfo.
- LUL, PriMap, SecMap
Coverage isn't perfect, but it gets the major things I found via DMD on Linux.
Example output in about:memory:
├──151.21 MB (49.73%) -- profiler
│ ├──141.49 MB (46.53%) ── lul
│ └────9.72 MB (03.20%) ── sampler
--HG--
extra : rebase_source : 67d2ada42aead43f68f5100a08204a1d1f1cfceb
