kernel/linux.git/tools/tracing/rtla/src/timerlat.c, branch v7.1-rc5

rtla/timerlat: Simplify RTLA_NO_BPF environment variable check

2026-03-11T14:29:50+00:00

The code that checks the RTLA_NO_BPF environment variable calls getenv() twice and uses strncmp() with a length of 2 to compare against the single-character string "1". This is inefficient and the comparison length is unnecessarily long. Store the result of getenv() in a local variable to avoid the redundant call, and replace strncmp() with strncmp_static() for the exact match comparison. This follows the same pattern established in recent commits that improved string comparison consistency throughout the rtla codebase. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-15-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Use str_has_prefix() for option prefix check

2026-03-11T14:29:50+00:00

The argument parsing code in timerlat_main() and osnoise_main() uses strncmp() with a length of 1 to check if the first argument starts with a dash, indicating an option flag was passed. Replace this pattern with str_has_prefix() for consistency with the rest of the codebase. While character comparison would be slightly more efficient, using str_has_prefix() provides better readability and maintains a uniform coding style throughout the rtla tool. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-14-wander@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Remove unneeded nr_cpus from for_each_monitored_cpu

2026-03-09T07:49:17+00:00

nr_cpus does not change at runtime, so passing it through the macro argument is unnecessary. Remove the argument and use the global nr_cpus instead. Signed-off-by: Costa Shulyupin Link: https://lore.kernel.org/r/20260306194953.2511960-5-costa.shul@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Consolidate nr_cpus usage across all tools

2026-03-09T07:49:16+00:00

sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects cpu_possible_mask, which is fixed at boot time, so querying it repeatedly is unnecessary. Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single global nr_cpus variable initialized once at startup. `#pragma once` in timerlat_u.h is needed for pre-C23 compilers to avoid redefinition errors. Signed-off-by: Costa Shulyupin Link: https://lore.kernel.org/r/20260306194953.2511960-2-costa.shul@redhat.com Signed-off-by: Tomas Glozar

rtla/timerlat: Add --stack-format option

2026-03-04T14:51:56+00:00

In the current implementation, the auto-analysis code for printing the stack captured in the tracefs buffer of the aa instance stops at the first encountered address that cannot be resolved into a function symbol. This is not always the desired behavior on all platforms; sometimes, there might be resolvable entries after unresolvable ones, and sometimes, the user might want to inspect the raw pointers for the unresolvable entries. Add a new option, --stack-format, with three values: - truncate: stop at first unresolvable entry. This is the current behavior, and is kept as the default. - skip: skip unresolvable entries, but do not stop on them. - full: print all entries, including unresolvable ones. To make this work, the "size" field of the stack entry is now also read and used as the maximum number of entries to print, capped at 64, since that is the fixed length of the "caller" field. Link: https://lore.kernel.org/r/20260119115222.744150-1-tglozar@redhat.com Signed-off-by: Tomas Glozar

rtla: Remove unused headers

2026-01-07T14:57:55+00:00

Remove unused includes for and to clean up the code and reduce unnecessary dependencies. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260106133655.249887-12-wander@redhat.com Signed-off-by: Tomas Glozar

rtla/timerlat: Add --bpf-action option

2026-01-07T14:57:16+00:00

Add option --bpf-action that allows the user to attach an external BPF program that will be executed via BPF tail call on latency threshold overflow. Executing additional BPF code on latency threshold overflow allows doing low-latency and in-kernel troubleshooting of the cause of the overflow. The option takes an argument, which is a path to a BPF ELF file expected to contain a function named "action_handler" in a section named "tp/timerlat_action" (the section is necessary for libbpf to assign the correct BPF program type to it). Link: https://lore.kernel.org/r/20251126144205.331954-3-tglozar@redhat.com Signed-off-by: Tomas Glozar

rtla: Set stop threshold after all instances are enabled

2026-01-07T14:57:15+00:00

This avoids startup races where one of the instances hit a threshold before all instances were enabled, and thus tracing stops without the relevant event. In particular, this is not uncommon with the tests that set a very tight threshold and then complain if there's no analysis. This also ensures that we don't stop tracing during a warmup. The downside is a small chance of having an event over the threshold early in the output, without stopping on it, which could cause user confusion. This should be less likely if the warmup feature is used, but that doesn't eliminate the race window, just the odds of an unusual spike right at that moment. Signed-off-by: Crystal Wood Link: https://lore.kernel.org/r/20251112152529.956778-6-crwood@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Fix unassigned nr_cpus

2025-11-20T12:15:54+00:00

In recently introduced timerlat_free(), the variable 'nr_cpus' is not assigned. Assign it with sysconf(_SC_NPROCESSORS_CONF) as done elsewhere. Remove the culprit: -Wno-maybe-uninitialized. The rest of the code is clean. Signed-off-by: Costa Shulyupin Reviewed-by: Tomas Glozar Fixes: 2f3172f9dd58 ("tools/rtla: Consolidate code between osnoise/timerlat and hist/top") Link: https://lore.kernel.org/r/20251002170846.437888-1-costa.shul@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Add for_each_monitored_cpu() helper

2025-11-20T12:15:53+00:00

The rtla tools have many instances of iterating over CPUs while checking if they are monitored. Add a for_each_monitored_cpu() helper macro to make the code more readable and reduce code duplication. Signed-off-by: Costa Shulyupin Reviewed-by: Tomas Glozar Link: https://lore.kernel.org/r/20251002123553.389467-1-costa.shul@redhat.com Signed-off-by: Tomas Glozar