Loading Documentation/tracers/mmiotrace.txt +19 −8 Original line number Original line Diff line number Diff line Loading @@ -25,7 +25,8 @@ Mmiotrace feature is compiled in by the CONFIG_MMIOTRACE option. Tracing is disabled by default, so it is safe to have this set to yes. SMP systems are disabled by default, so it is safe to have this set to yes. SMP systems are supported, but tracing is unreliable and may miss events if more than one CPU supported, but tracing is unreliable and may miss events if more than one CPU is on-line, therefore mmiotrace takes all but one CPU off-line during run-time is on-line, therefore mmiotrace takes all but one CPU off-line during run-time activation [not implemented]. activation. You can re-enable CPUs by hand, but you have been warned, there is no way to automatically detect if you are losing events due to CPUs racing. Usage Quick Reference Usage Quick Reference Loading @@ -37,7 +38,7 @@ $ cat /debug/tracing/trace_pipe > mydump.txt & Start X or whatever. Start X or whatever. $ echo "X is up" > /debug/tracing/marker $ echo "X is up" > /debug/tracing/marker $ echo none > /debug/tracing/current_tracer $ echo none > /debug/tracing/current_tracer Check kernel log. Check for lost events. Usage Usage Loading Loading @@ -67,12 +68,22 @@ do. Shut down mmiotrace (requires root privileges): Shut down mmiotrace (requires root privileges): $ echo none > /debug/tracing/current_tracer $ echo none > /debug/tracing/current_tracer The 'cat' process exits. If it does not, kill it by 'fg' and pressing ctrl+c. The 'cat' process exits. If it does not, kill it by issuing 'fg' command and pressing ctrl+c. [This feature is not implemented yet!] Check your kernel log. If there are messages about mmiotrace losing events, Check that mmiotrace did not lose events due to a buffer filling up. Either this is due to buffer overrun, and the trace is incomplete. You should enlarge $ grep -i lost mydump.txt the buffers and try again. [How?] which tells you exactly how many events were lost, or use $ dmesg to view your kernel log and look for "mmiotrace has lost events" warning. If events were lost, the trace is incomplete. You should enlarge the buffers and try again. Buffers are enlarged by first seeing how large the current buffers are: $ cat /debug/tracing/trace_entries gives you a number. Approximately double this number and write it back, for instance: $ echo 128000 > /debug/tracing/trace_entries Then start again from the top. If you are doing a trace for a driver project, e.g. Nouveau, you should also If you are doing a trace for a driver project, e.g. Nouveau, you should also do the following before sending your results: do the following before sending your results: Loading Loading
Documentation/tracers/mmiotrace.txt +19 −8 Original line number Original line Diff line number Diff line Loading @@ -25,7 +25,8 @@ Mmiotrace feature is compiled in by the CONFIG_MMIOTRACE option. Tracing is disabled by default, so it is safe to have this set to yes. SMP systems are disabled by default, so it is safe to have this set to yes. SMP systems are supported, but tracing is unreliable and may miss events if more than one CPU supported, but tracing is unreliable and may miss events if more than one CPU is on-line, therefore mmiotrace takes all but one CPU off-line during run-time is on-line, therefore mmiotrace takes all but one CPU off-line during run-time activation [not implemented]. activation. You can re-enable CPUs by hand, but you have been warned, there is no way to automatically detect if you are losing events due to CPUs racing. Usage Quick Reference Usage Quick Reference Loading @@ -37,7 +38,7 @@ $ cat /debug/tracing/trace_pipe > mydump.txt & Start X or whatever. Start X or whatever. $ echo "X is up" > /debug/tracing/marker $ echo "X is up" > /debug/tracing/marker $ echo none > /debug/tracing/current_tracer $ echo none > /debug/tracing/current_tracer Check kernel log. Check for lost events. Usage Usage Loading Loading @@ -67,12 +68,22 @@ do. Shut down mmiotrace (requires root privileges): Shut down mmiotrace (requires root privileges): $ echo none > /debug/tracing/current_tracer $ echo none > /debug/tracing/current_tracer The 'cat' process exits. If it does not, kill it by 'fg' and pressing ctrl+c. The 'cat' process exits. If it does not, kill it by issuing 'fg' command and pressing ctrl+c. [This feature is not implemented yet!] Check your kernel log. If there are messages about mmiotrace losing events, Check that mmiotrace did not lose events due to a buffer filling up. Either this is due to buffer overrun, and the trace is incomplete. You should enlarge $ grep -i lost mydump.txt the buffers and try again. [How?] which tells you exactly how many events were lost, or use $ dmesg to view your kernel log and look for "mmiotrace has lost events" warning. If events were lost, the trace is incomplete. You should enlarge the buffers and try again. Buffers are enlarged by first seeing how large the current buffers are: $ cat /debug/tracing/trace_entries gives you a number. Approximately double this number and write it back, for instance: $ echo 128000 > /debug/tracing/trace_entries Then start again from the top. If you are doing a trace for a driver project, e.g. Nouveau, you should also If you are doing a trace for a driver project, e.g. Nouveau, you should also do the following before sending your results: do the following before sending your results: Loading
Pekka Paalanen <pq@iki.fi> Signed-off-by:
Ingo Molnar <mingo@elte.hu>