Last iteration left two candidates for why trace_gpu_stream produced no
file: the CLI flag not reaching the cvar, or BeginTracing failing
silently. Neither. Following the code instead of guessing:
BeginTracing only sets trace_state_ = kStreaming ("Streaming starts on
the next primary buffer execute"). The file is opened later, in
ExecutePrimaryBuffer, inside
#if XE_ENABLE_TRACE_WRITER_INSTRUMENTATION == 1
and trace_writer.h defines that as 0 under NDEBUG, 1 otherwise -- the
trace writer exists only in debug builds.
Confirmed against the binaries, with a control. The format string
"{:08X}_stream.xtr" lives only inside that guard:
build/bin/Linux/Release/xenia_canary 0 occurrences
build/bin/Linux/Debug/xenia_canary 1 occurrence
/sylph-home/re/canary-build/.../Release/... 0 <- what run-canary uses
The debug binary is the control: it proves the test finds the string when
it is present, so the release zero means something.
So trace_gpu_stream is a no-op in this container's emulator -- the cvar
parses, BeginTracing runs, and nothing can open a file. The kill -9 was
not the cause either, though it would have destroyed a trace had one
existed.
The route exists but is not cheap: a debug build with the writer compiled
in sits at build/bin/Linux/Debug/xenia_canary, 253 MB against Release's
18 MB, so a much slower boot plus a trace of every GPU packet on a disk
at 95%. Recorded as available rather than attempted -- what it would
confirm, the DC_LUT write, is already a well-supported inference, and the
cost is out of proportion to the gain.
METHOD: a cvar existing does not mean the feature is compiled in; and
test a compile-time gate against the binary, with a control.
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