From: Tomas Glozar <tglo...@redhat.com>
rtla-timerlat allows reducing latency on wake up from idle by setting /dev/cpu_dma_latency during the timerlat measurement. This has an effect on the idle states of all CPUs, including those which are not used by timerlat. Add option --deepest-idle-state that allows limiting the idle state only on cpus where the timerlat measurement is running. libcpupower is used to do the disabling of idle states via the corresponding sysfs interface. v2: - Split patch adding dependency on libcpupower to two patches, one for libcpupower detection and one for rtla libcpupower dependency. - Make building against libcpupower optional. rtla will throw an error when built without libcpupower and --deepest-idle-state is used. - Rename option from --disable-idle-states to --deepest-idle-state and add an argument to choose the deepest idle state the CPU is allowed to get into. -1 can be used to disable all idle states: this is useful on non-ACPI platforms, where idle state 0 can be an actual idle state with an exit latency rather than a representation of an active CPU, as with the ACPI C0 state. Note: It is also possible to retrieve the latency for individual idle states of a cpu by calling cpuidle_state_latency. This could be used to implement another rtla option that would take the maximum latency, like --dma-latency does, and which would only take effect on CPUs used by timerlat. My opinion is that this proposed feature should not replace either --dma-latency nor --deepest-idle-state. For the former, there might be systems which have /dev/cpu_dma_latency but don't have a cpuidle implementation; for the latter, in many cases the user will want to set the idle state rather than the latency itself. v3: - Remove unneeded NULL check before free in restore_cpu_idle_disable_state and free_cpu_idle_disable_states. - Check for calloc() returning NULL in save_cpu_idle_disable_state. - Check for saved_cpu_idle_disable_state existing in restore_cpu_idle_disable_state. - Implement dummy functions for libcpupower functionality if libcpupower is not present during build. That allows libcpupower presence to be checked through a special function at one place instead of using several #ifdefs. - Only call sysconf() once when iterating through all CPUs. Note that there are a few instances in the original code which keep on calling sysconf() multiple times; fixing that is for another patch. Tomas Glozar (6): tools/build: Add libcpupower dependency detection rtla: Add optional dependency on libcpupower rtla/utils: Add idle state disabling via libcpupower rtla/timerlat: Add --deepest-idle-state for top rtla/timerlat: Add --deepest-idle-state for hist rtla: Documentation: Mention --deepest-idle-state .../tools/rtla/common_timerlat_options.rst | 8 + tools/build/Makefile.feature | 1 + tools/build/feature/Makefile | 4 + tools/tracing/rtla/Makefile | 2 + tools/tracing/rtla/Makefile.config | 10 ++ tools/tracing/rtla/README.txt | 4 + tools/tracing/rtla/src/timerlat_hist.c | 42 ++++- tools/tracing/rtla/src/timerlat_top.c | 42 ++++- tools/tracing/rtla/src/utils.c | 148 ++++++++++++++++++ tools/tracing/rtla/src/utils.h | 13 ++ 10 files changed, 272 insertions(+), 2 deletions(-) -- 2.46.0
