Misattributed samples are strictly related to handlers, and the size
of this special group helps understand how accurate the profile is.
For these reasons, it makes more sense to always show this group.
LOG=N
BUG=v8:4899
Review URL: https://codereview.chromium.org/1895793002
Cr-Commit-Position: refs/heads/master@{#35585}
A new script is introduced, linux_perf_report.py, which reads Linux perf
data collected when running with FLAG_perf_basic_prof enabled and
produces an input file for flamegraph.pl, or a report of the hottest
bytecode handlers.
The bottom blocks of the produced flamegraph are bytecode handlers.
Special bottom blocks exist as well for compile routines, time spent
outside the interpreter and interpreter entry trampolines.
Because various Stubs and other pieces of JITted code do not maintain the
frame pointer, some sampled callchains might be incomplete even if V8 is
compiled with no_omit_framepointer=on. The script is able to detect the
most common anomaly where an entry trampoline appears in a chain, but not
on top, meaning that the frame of another bytecode handler is hidden. In
this case, the sample will be moved to a [misattributed] group to avoid
skewing the profile of unrelated handlers.
Misattributed samples and compilation routines are hidden by default.
BUG=v8:4899
LOG=N
Review URL: https://codereview.chromium.org/1783503002
Cr-Commit-Position: refs/heads/master@{#35574}
