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| -rw-r--r-- | docs/devel/tracing.rst | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst index f7e589f67c..4ebf8e38ea 100644 --- a/docs/devel/tracing.rst +++ b/docs/devel/tracing.rst @@ -11,22 +11,22 @@ for debugging, profiling, and observing execution. Quickstart ========== -1. Build with the 'simple' trace backend:: - - ./configure --enable-trace-backends=simple - make - -2. Create a file with the events you want to trace:: - - echo memory_region_ops_read >/tmp/events +Enable tracing of ``memory_region_ops_read`` and ``memory_region_ops_write`` +events:: -3. Run the virtual machine to produce a trace file:: + $ qemu --trace "memory_region_ops_*" ... + ... + 719585@1608130130.441188:memory_region_ops_read cpu 0 mr 0x562fdfbb3820 addr 0x3cc value 0x67 size 1 + 719585@1608130130.441190:memory_region_ops_write cpu 0 mr 0x562fdfbd2f00 addr 0x3d4 value 0x70e size 2 - qemu --trace events=/tmp/events ... # your normal QEMU invocation +This output comes from the "log" trace backend that is enabled by default when +``./configure --enable-trace-backends=BACKENDS`` was not explicitly specified. -4. Pretty-print the binary trace file:: +More than one trace event pattern can be specified by providing a file +instead:: - ./scripts/simpletrace.py trace-events-all trace-* # Override * with QEMU <pid> + $ echo "memory_region_ops_*" >/tmp/events + $ qemu --trace events=/tmp/events ... Trace events ============ @@ -195,7 +195,7 @@ script. The trace backends are chosen at configure time:: - ./configure --enable-trace-backends=simple + ./configure --enable-trace-backends=simple,dtrace For a list of supported trace backends, try ./configure --help or see below. If multiple backends are enabled, the trace is sent to them all. @@ -227,10 +227,11 @@ uses DPRINTF(). Simpletrace ----------- -The "simple" backend supports common use cases and comes as part of the QEMU -source tree. It may not be as powerful as platform-specific or third-party -trace backends but it is portable. This is the recommended trace backend -unless you have specific needs for more advanced backends. +The "simple" backend writes binary trace logs to a file from a thread, making +it lower overhead than the "log" backend. A Python API is available for writing +offline trace file analysis scripts. It may not be as powerful as +platform-specific or third-party trace backends but it is portable and has no +special library dependencies. Monitor commands ~~~~~~~~~~~~~~~~ |