6.5-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Bristot de Oliveira bristot@kernel.org
[ Upstream commit 301deca09b254965661d3e971f1a60ac2ce41f5f ]
timerlat auto-analysis takes note of all IRQs, before or after the execution of the timerlat thread.
Because we cannot go backward in the trace (we will fix it when moving to trace-cmd lib?), timerlat aa take note of the last IRQ execution in the waiting for the IRQ state, and then print it if it is executed after the expected timer IRQ starting time.
After the thread sample, the timerlat starts recording the next IRQs as "previous" irq for the next occurrence.
However, if an IRQ happens after the thread measurement but before the tracing stops, it is classified as a previous IRQ. That is not wrong, as it can be "previous" for the subsequent activation. What is wrong is considering it as a potential source for the last activation.
Ignore the IRQ interference that happens after the IRQ starting time for now. A future improvement for timerlat can be either keeping a list of previous IRQ execution or using the trace-cmd library. Still, it requires further investigation - it is a new feature.
Link: https://lore.kernel.org/lkml/a44a3f5c801dcc697bacf7325b65d4a5b0460537.169116...
Fixes: 27e348b221f6 ("rtla/timerlat: Add auto-analysis core") Signed-off-by: Daniel Bristot de Oliveira bristot@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/tracing/rtla/src/timerlat_aa.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c index baf1efda0581d..7093fd5333beb 100644 --- a/tools/tracing/rtla/src/timerlat_aa.c +++ b/tools/tracing/rtla/src/timerlat_aa.c @@ -545,7 +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;
@@ -562,12 +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) - printf(" Previous IRQ interference: \t\t up to %9.2f us\n", - ns_to_usf(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.