Profiling with Instruments¶
Instruments can be used for memory profiling and for statistical profiling.
Official Apple documentation¶
Select “Time Profiler” from the “Choose a profiling template for:” dialog.
In the top left, next to the record and pause button, there will be a “[machine name] > All Processes”. Click “All Processes” and select “firefox” from the “Running Applications” section.
Click the record button (red circle in top left)
Wait for the amount of time that you want to profile
Click the stop button
Command line tools¶
How do we monitor performance counters (cache miss etc.)? Instruments has a “Counters” instrument that can do this.
Instruments will record a call stack at each allocation point. The call
tree view can be quite helpful here. Switch from “Statistics”. This
malloc profiling is done using the
MallocStackLogging). Currently this means you need to
build with jemalloc disabled (
ac_add_options --disable-jemalloc). You
also need the fix to Bug
Under “File” -> “Recording Options” you can enable “Record Kernel Callstacks”. To get full symbols and not just the exported ones, you’ll to install the matching Kernel Debug Kit. Make sure you install the one whose macOS version exactly matches your version, including the identifier at the end (e.g. “12.3.1 (21E258)”).
Allow Instruments to find kernel symbols¶
Installing the KDK is often not enough for Instruments to find the symbols. Instruments uses Spotlight to find the dSYMs with the matching UUID, so you need to put the dSYM in a place where Spotlight will index it.
First, check the UUID of your macOS installation’s kernel. To do so, run the following:
% dwarfdump --uuid /System/Library/Kernels/kernel.release.t6000 UUID: C342869F-FFB9-3CCE-A5A3-EA711C1E87F6 (arm64e) /System/Library/Kernels/kernel.release.t6000
Then, find the corresponding dSYM file in the KDK that you installed, and
mdls on it. For example:
% mdls /Library/Developer/KDKs/KDK_12.3.1_21E258.kdk/System/Library/Kernels/kernel.release.t6000.dSYM
(Make sure you use the
.release variant, not the
or any of the others.)
If the output from
mdls contains the string
and the UUID matches, you’re done.
Otherwise, try copying the
kernel.release.t6000.dSYM bundle to your home
directory, and then run
mdls on the copied file. For example:
% cp -r /Library/Developer/KDKs/KDK_12.3.1_21E258.kdk/System/Library/Kernels/kernel.release.t6000.dSYM ~/ % mdls ~/kernel.release.t6000.dSYM _kMDItemDisplayNameWithExtensions = "kernel.release.t6000.dSYM" com_apple_xcode_dsym_paths = ( "Contents/Resources/DWARF/kernel.release.t6000" ) com_apple_xcode_dsym_uuids = ( "C342869F-FFB9-3CCE-A5A3-EA711C1E87F6" ) kMDItemContentCreationDate = 2022-03-21 15:25:57 +0000 [...]
Now Instruments should be able to pick up the kernel symbols.
DTPerformanceSession api can be used to control profiling from
applications like the old CHUD API we use in Shark builds. Bug
System Trace might be useful.