From a23c05fd76cf4ad27e0c74f7a93e7b089e94a55c Mon Sep 17 00:00:00 2001 From: Daniel Bristot de Oliveira Date: Tue, 6 Feb 2024 15:32:06 +0100 Subject: tools/rtla: Add -U/--user-load option to timerlat The timerlat tracer provides an interface for any application to wait for the timerlat's periodic wakeup. Currently, rtla timerlat uses it to dispatch its user-space workload (-u option). But as the tracer interface is generic, rtla timerlat can also be used to monitor any workload that uses it. For example, a user might place their own workload to wait on the tracer interface, and monitor the results with rtla timerlat. Add the -U option to rtla timerlat top and hist. With this option, rtla timerlat will not dispatch its workload but only setting up the system, waiting for a user to dispatch its workload. The sample code in this patch is an example of python application that loops in the timerlat tracer fd. To use it, dispatch: # rtla timerlat -U In a terminal, then run the python program on another terminal, specifying the CPU to run it. For example, setting on CPU 1: #./timerlat_load.py 1 Then rtla timerlat will start printing the statistics of the ./timerlat_load.py app. An interesting point is that the "Ret user Timer Latency" value is the overall response time of the load. The sample load does a memory copy to exemplify that. The stop tracing options on rtla timerlat works in this setup as well, including auto analysis. Link: https://lkml.kernel.org/r/36e6bcf18fe15c7601048fd4c65aeb193c502cc8.1707229706.git.bristot@kernel.org Cc: Jonathan Corbet Cc: Masami Hiramatsu Signed-off-by: Daniel Bristot de Oliveira --- Documentation/tools/rtla/common_timerlat_options.rst | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation') diff --git a/Documentation/tools/rtla/common_timerlat_options.rst b/Documentation/tools/rtla/common_timerlat_options.rst index 88506b397c2dd..d3255ed70195f 100644 --- a/Documentation/tools/rtla/common_timerlat_options.rst +++ b/Documentation/tools/rtla/common_timerlat_options.rst @@ -33,3 +33,9 @@ to wait on the timerlat_fd. Once the workload is awakes, it goes to sleep again adding so the measurement for the kernel-to-user and user-to-kernel to the tracer output. + +**-U**, **--user-load** + + Set timerlat to run without workload, waiting for the user to dispatch a per-cpu + task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd. + See linux/tools/rtla/sample/timerlat_load.py for an example of user-load code. -- cgit 1.2.3-korg