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LLVM has some utilities to print statistics about PGO data. Let's print a few views so we can better debug PGO instrumentation.
This is more reliable. See comment in added patch for context.
Contrary to popular belief, the system doesn't need to be "idle" to collect profiling data. See inline comment + https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp for the PGO implementation for the evidence.
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geofft
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Mar 23, 2026
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| %p expands to the process ID. While unlikely, PID collisions can occur, | ||
| leading to loss of data. |
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Did you actually run into a collision? Especially in our CI runners we shouldn't have so many things running to trigger PID reuse, and it's easy to bump the max PID number (the kernel default is low for human friendliness but I think it can go up to at least 2^31). But no actual objection to this patch, especially if it's upstreamed at some point.
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No. But I plan to enable PGO training against the full test harness in the near future and this will increase probability of a collision.
PID based naming alone isn't reliable and I wanted to change this out of principle.
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Can we create some issues for upstreaming per #886 |
This was referenced Mar 24, 2026
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Some of these are good candidates for up-streaming. Although we make assumptions about availability of [modern] LLVM. So upstream patches may require configure work to sniff toolchain capabilities. It was vastly easier to implement the simple patches in PBS first.