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Allow printing task backtraces via profiling peek mechanism #56043

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Allow printing task backtraces via profiling peek mechanism #56043

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5 changes: 5 additions & 0 deletions base/Base.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -601,6 +601,11 @@ function profile_printing_listener()
profile = @something(profile, require(PkgId(UUID("9abbd945-dff8-562f-b5e8-e1ebf5ef1b79"), "Profile")))

invokelatest(profile.peek_report[])
if Base.get_bool_env("JULIA_PROFILE_PEEK_TASK_BACKTRACES", true) === true
print(stderr, "Printing Julia task backtraces...\n")
flush(stderr)
ccall(:jl_print_task_backtraces, Cvoid, ())
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This prints to a different abstraction over stderr than the other println calls here, so may need to explicitly call flush around it to ensure the output doesn't get jumbled

Aside, it can also be better to use print(stderr, "<text>\n") instead of println where reliable async behavior is desired, since it ensures the whole text prints in the same syscall

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This is very helpful, thanks!

end
if Base.get_bool_env("JULIA_PROFILE_PEEK_HEAP_SNAPSHOT", false) === true
println(stderr, "Saving heap snapshot...")
fname = invokelatest(profile.take_heap_snapshot)
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7 changes: 6 additions & 1 deletion doc/src/manual/environment-variables.md
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Expand Up @@ -445,7 +445,12 @@ Enable debug logging for a file or module, see [`Logging`](@ref man-logging) for

### [`JULIA_PROFILE_PEEK_HEAP_SNAPSHOT`](@id JULIA_PROFILE_PEEK_HEAP_SNAPSHOT)

Enable collecting of a heap snapshot during execution via the profiling peek mechanism.
Enable collecting of a heap snapshot during execution via the profiling peek mechanism. Set to `1` to enable.
See [Triggered During Execution](@ref).

### [`JULIA_PROFILE_PEEK_TASK_BACKTRACES`](@id JULIA_PROFILE_PEEK_TASK_BACKTRACES)

Disable printing of task backtraces via the profiling peek mechanism. Set to `0` to disable.
See [Triggered During Execution](@ref).

### [`JULIA_TIMING_SUBSYSTEMS`](@id JULIA_TIMING_SUBSYSTEMS)
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3 changes: 3 additions & 0 deletions stdlib/Profile/docs/src/index.md
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Expand Up @@ -34,6 +34,9 @@ First, a single stack trace at the instant that the signal was thrown is shown,
followed by the profile report at the next yield point, which may be at task completion for code without yield points
e.g. tight loops.

In addition to the profile, all task backtraces will be printed, unless the environment variable
[`JULIA_PROFILE_PEEK_TASK_BACKTRACES`](@ref JULIA_PROFILE_PEEK_TASK_BACKTRACES) is set to `0`.

Optionally set environment variable [`JULIA_PROFILE_PEEK_HEAP_SNAPSHOT`](@ref JULIA_PROFILE_PEEK_HEAP_SNAPSHOT) to `1` to also automatically collect a
[heap snapshot](@ref Heap-Snapshots).

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