[Lldb-commits] [PATCH] D129257: [trace][intel pt] Add a cgroup filter

[walter erquinigo via Phabricator via lldb-commits]

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It turns out that cgroup filtering is relatively trivial and works
really nicely. Thid diffs adds automatic cgroup filtering when in
per-cpu mode, unless a new --disable-cgroup-filtering flag is passed in
the start command. At least on Meta machines, all processes are spawned
inside a cgroup by default, which comes super handy, because per cpu
tracing is now much more precise.

A manual test gave me this result

- Without filtering: Total number of trace items: 36083 Total number of continuous executions found: 229 Number of continuous executions for this thread: 2 Total number of PSB blocks found: 98 Number of PSB blocks for this thread 2 Total number of unattributed PSB blocks found: 38

- With filtering: Total number of trace items: 87756 Total number of continuous executions found: 123 Number of continuous executions for this thread: 2 Total number of PSB blocks found: 10 Number of PSB blocks for this thread 3 Total number of unattributed PSB blocks found: 2

Filtering gives us great results. The number of instructions collected
more than double (probalby because we have less noise in the trace), and
we have much less unattributed PSBs blocks and unrelated PSBs in
general. The ones that are unrelated probably belong to other processes
in the same cgroup.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129257

Files:
  lldb/include/lldb/Utility/TraceIntelPTGDBRemotePackets.h
  lldb/source/Plugins/Process/Linux/IntelPTCollector.cpp
  lldb/source/Plugins/Process/Linux/IntelPTMultiCoreTrace.cpp
  lldb/source/Plugins/Process/Linux/IntelPTMultiCoreTrace.h
  lldb/source/Plugins/Process/Linux/IntelPTSingleBufferTrace.cpp
  lldb/source/Plugins/Process/Linux/IntelPTSingleBufferTrace.h
  lldb/source/Plugins/Trace/intel-pt/CommandObjectTraceStartIntelPT.cpp
  lldb/source/Plugins/Trace/intel-pt/CommandObjectTraceStartIntelPT.h
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPT.cpp
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPT.h
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPTConstants.h
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPTMultiCpuDecoder.cpp
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPTMultiCpuDecoder.h
  lldb/source/Plugins/Trace/intel-pt/TraceIntelPTOptions.td
  lldb/source/Utility/TraceIntelPTGDBRemotePackets.cpp

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