Commit 3006adf3 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'rtla-v6.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bristot/linux 

Pull rtla fixes from Daniel Bristot de Oliveira:
 "rtla (Real-Time Linux Analysis) tool fixes.

  Timerlat auto-analysis:

   - Timerlat is reporting thread interference time without thread noise
     events occurrence. It was caused because the thread interference
     variable was not reset after the analysis of a timerlat activation
     that did not hit the threshold.

   - The IRQ handler delay is estimated from the delta of the IRQ
     latency reported by timerlat, and the timestamp from IRQ handler
     start event. If the delta is near-zero, the drift from the external
     clock and the trace event and/or the overhead can cause the value
     to be negative. If the value is negative, print a zero-delay.

   - IRQ handlers happening after the timerlat thread event but before
     the stop tracing were being reported as IRQ that happened before
     the *current* IRQ occurrence. Ignore Previous IRQ noise in this
     condition because they are valid only for the *next* timerlat
     activation.

  Timerlat user-space:

   - Timerlat is stopping all user-space thread if a CPU becomes
     offline. Do not stop the entire tool if a CPU is/become offline,
     but only the thread of the unavailable CPU. Stop the tool only, if
     all threads leave because the CPUs become/are offline.

  man-pages:

   - Fix command line example in timerlat hist man page"

* tag 'rtla-v6.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bristot/linux:
  rtla: fix a example in rtla-timerlat-hist.rst
  rtla/timerlat: Do not stop user-space if a cpu is offline
  rtla/timerlat_aa: Fix previous IRQ delay for IRQs that happens after thread sample
  rtla/timerlat_aa: Fix negative IRQ delay
  rtla/timerlat_aa: Zero thread sum after every sample analysis
parents ba7d997a 81ec384b

Documentation/tools/rtla/rtla-timerlat-hist.rst

+2 −2
Original line number Diff line number Diff line
@@ -36,11 +36,11 @@ EXAMPLE 
In the example below, **rtla timerlat hist** is set to run for *10* minutes,

in the cpus *0-4*, *skipping zero* only lines. Moreover, **rtla timerlat

hist** will change the priority of the *timerlat* threads to run under

*SCHED_DEADLINE* priority, with a *10us* runtime every *1ms* period. The

*SCHED_DEADLINE* priority, with a *100us* runtime every *1ms* period. The

*1ms* period is also passed to the *timerlat* tracer. Auto-analysis is disabled

to reduce overhead ::



  [root@alien ~]# timerlat hist -d 10m -c 0-4 -P d:100us:1ms -p 1ms --no-aa

  [root@alien ~]# timerlat hist -d 10m -c 0-4 -P d:100us:1ms -p 1000 --no-aa

  # RTLA timerlat histogram

  # Time unit is microseconds (us)

  # Duration:   0 00:10:00

tools/tracing/rtla/src/timerlat_aa.c

+26 −6
Original line number Diff line number Diff line
@@ -159,6 +159,7 @@ static int timerlat_aa_irq_latency(struct timerlat_aa_data *taa_data, 
	taa_data->thread_nmi_sum = 0;

	taa_data->thread_irq_sum = 0;

	taa_data->thread_softirq_sum = 0;

	taa_data->thread_thread_sum = 0;

	taa_data->thread_blocking_duration = 0;

	taa_data->timer_irq_start_time = 0;

	taa_data->timer_irq_duration = 0;
@@ -337,7 +338,23 @@ static int timerlat_aa_irq_handler(struct trace_seq *s, struct tep_record *recor 
		taa_data->timer_irq_start_time = start;

		taa_data->timer_irq_duration = duration;



		/*

		 * We are dealing with two different clock sources: the

		 * external clock source that timerlat uses as a reference

		 * and the clock used by the tracer. There are also two

		 * moments: the time reading the clock and the timer in

		 * which the event is placed in the buffer (the trace

		 * event timestamp). If the processor is slow or there

		 * is some hardware noise, the difference between the

		 * timestamp and the external clock read can be longer

		 * than the IRQ handler delay, resulting in a negative

		 * time. If so, set IRQ start delay as 0. In the end,

		 * it is less relevant than the noise.

		 */

		if (expected_start < taa_data->timer_irq_start_time)

			taa_data->timer_irq_start_delay = taa_data->timer_irq_start_time - expected_start;

		else

			taa_data->timer_irq_start_delay = 0;



		/*

		 * not exit from idle.
@@ -528,7 +545,7 @@ static int timerlat_aa_kworker_start_handler(struct trace_seq *s, struct tep_rec 
static void timerlat_thread_analysis(struct timerlat_aa_data *taa_data, int cpu,

				     int irq_thresh, int thread_thresh)

{

	unsigned long long exp_irq_ts;

	long long exp_irq_ts;

	int total;

	int irq;
@@ -545,12 +562,15 @@ static void timerlat_thread_analysis(struct timerlat_aa_data *taa_data, int cpu, 


	/*

	 * Expected IRQ arrival time using the trace clock as the base.

	 *

	 * TODO: Add a list of previous IRQ, and then run the list backwards.

	 */

	exp_irq_ts = taa_data->timer_irq_start_time - taa_data->timer_irq_start_delay;



	if (exp_irq_ts < taa_data->prev_irq_timstamp + taa_data->prev_irq_duration)

	if (exp_irq_ts < taa_data->prev_irq_timstamp + taa_data->prev_irq_duration) {

		if (taa_data->prev_irq_timstamp < taa_data->timer_irq_start_time)

			printf("  Previous IRQ interference:	\t\t up to  %9.2f us\n",

				ns_to_usf(taa_data->prev_irq_duration));

	}



	/*

	 * The delay that the IRQ suffered before starting.

tools/tracing/rtla/src/timerlat_u.c

+4 −2
Original line number Diff line number Diff line
@@ -45,7 +45,7 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params) 


	retval = sched_setaffinity(gettid(), sizeof(set), &set);

	if (retval == -1) {

		err_msg("Error setting user thread affinity\n");

		debug_msg("Error setting user thread affinity %d, is the CPU online?\n", cpu);

		exit(1);

	}
@@ -193,6 +193,8 @@ void *timerlat_u_dispatcher(void *data) 
					procs_count--;

				}

			}



			if (!procs_count)

				break;

		}