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author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-04 18:19:55 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-04 18:19:55 -0700 |
commit | 3006adf3be79cde4d14b1800b963b82b6e5572e0 (patch) | |
tree | 10fde9241554e6e950791a54da087c4f1dff0882 | |
parent | ba7d997a2a29ee3fa766fee912c65796e0c21903 (diff) | |
parent | 81ec384b80ffbda752c230778d39ea620c7e3bcf (diff) | |
download | vfs-3006adf3be79cde4d14b1800b963b82b6e5572e0.tar.gz |
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
-rw-r--r-- | Documentation/tools/rtla/rtla-timerlat-hist.rst | 4 | ||||
-rw-r--r-- | tools/tracing/rtla/src/timerlat_aa.c | 32 | ||||
-rw-r--r-- | tools/tracing/rtla/src/timerlat_u.c | 6 |
3 files changed, 32 insertions, 10 deletions
diff --git a/Documentation/tools/rtla/rtla-timerlat-hist.rst b/Documentation/tools/rtla/rtla-timerlat-hist.rst index 057db78d4095a..03b7f3deb0698 100644 --- a/Documentation/tools/rtla/rtla-timerlat-hist.rst +++ b/Documentation/tools/rtla/rtla-timerlat-hist.rst @@ -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 diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c index e0ffe69c271c6..7093fd5333beb 100644 --- a/tools/tracing/rtla/src/timerlat_aa.c +++ b/tools/tracing/rtla/src/timerlat_aa.c @@ -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; - taa_data->timer_irq_start_delay = taa_data->timer_irq_start_time - expected_start; + /* + * 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) - 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. diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c index 05e310696dd5c..01dbf9a6b5a51 100644 --- a/tools/tracing/rtla/src/timerlat_u.c +++ b/tools/tracing/rtla/src/timerlat_u.c @@ -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); } @@ -193,7 +193,9 @@ void *timerlat_u_dispatcher(void *data) procs_count--; } } - break; + + if (!procs_count) + break; } sleep(1); |