Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'trace-latency-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing latency update from Steven Rostedt:
- Add TIMERLAT_ALIGN osnoise option
Add a timer alignment option for timerlat that makes it work like the
cyclictest -A option. timelat creates threads to test the latency of
the kernel. The alignment option will have these threads trigger at
the alignment offsets from each other. Instead of having each thread
wake up at the exact same time, if the alignment is set to "20" each
thread will wake up at 20 microseconds from the previous one.
* tag 'trace-latency-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing/osnoise: Add option to align tlat threads
+53
-1
+53
-1
kernel/trace/trace_osnoise.c
+53
-1
kernel/trace/trace_osnoise.c
···
58
58
OSN_PANIC_ON_STOP,
59
59
OSN_PREEMPT_DISABLE,
60
60
OSN_IRQ_DISABLE,
61
+
OSN_TIMERLAT_ALIGN,
61
62
OSN_MAX
62
63
};
63
64
···
67
66
"OSNOISE_WORKLOAD",
68
67
"PANIC_ON_STOP",
69
68
"OSNOISE_PREEMPT_DISABLE",
70
-
"OSNOISE_IRQ_DISABLE" };
69
+
"OSNOISE_IRQ_DISABLE",
70
+
"TIMERLAT_ALIGN" };
71
71
72
72
#define OSN_DEFAULT_OPTIONS 0x2
73
73
static unsigned long osnoise_options = OSN_DEFAULT_OPTIONS;
···
253
251
static DEFINE_PER_CPU(struct timerlat_variables, per_cpu_timerlat_var);
254
252
255
253
/*
254
+
* timerlat wake-up offset for next thread with TIMERLAT_ALIGN set.
255
+
*/
256
+
static atomic64_t align_next;
257
+
258
+
/*
256
259
* this_cpu_tmr_var - Return the per-cpu timerlat_variables on its relative CPU
257
260
*/
258
261
static inline struct timerlat_variables *this_cpu_tmr_var(void)
···
275
268
276
269
/* Synchronize with the timerlat interfaces */
277
270
mutex_lock(&interface_lock);
271
+
278
272
/*
279
273
* So far, all the values are initialized as 0, so
280
274
* zeroing the structure is perfect.
···
286
278
hrtimer_cancel(&tlat_var->timer);
287
279
memset(tlat_var, 0, sizeof(*tlat_var));
288
280
}
281
+
/*
282
+
* Reset also align_next, to be filled by a new offset by the first timerlat
283
+
* thread that wakes up, if TIMERLAT_ALIGN is set.
284
+
*/
285
+
atomic64_set(&align_next, 0);
286
+
289
287
mutex_unlock(&interface_lock);
290
288
}
291
289
#else /* CONFIG_TIMERLAT_TRACER */
···
340
326
u64 stop_tracing_total; /* stop trace in the final operation (report/thread) */
341
327
#ifdef CONFIG_TIMERLAT_TRACER
342
328
u64 timerlat_period; /* timerlat period */
329
+
u64 timerlat_align_us; /* timerlat alignment */
343
330
u64 print_stack; /* print IRQ stack if total > */
344
331
int timerlat_tracer; /* timerlat tracer */
345
332
#endif
···
353
338
#ifdef CONFIG_TIMERLAT_TRACER
354
339
.print_stack = 0,
355
340
.timerlat_period = DEFAULT_TIMERLAT_PERIOD,
341
+
.timerlat_align_us = 0,
356
342
.timerlat_tracer = 0,
357
343
#endif
358
344
};
···
1846
1830
tlat->abs_period = (u64) ktime_to_ns(next_abs_period);
1847
1831
1848
1832
/*
1833
+
* Align thread in the first cycle on each CPU to the set alignment
1834
+
* if TIMERLAT_ALIGN is set.
1835
+
*
1836
+
* This is done by using an atomic64_t to store the next absolute period.
1837
+
* The first thread that wakes up will set the atomic64_t to its
1838
+
* absolute period, and the other threads will increment it by
1839
+
* the alignment value.
1840
+
*/
1841
+
if (test_bit(OSN_TIMERLAT_ALIGN, &osnoise_options) && !tlat->count
1842
+
&& atomic64_cmpxchg_relaxed(&align_next, 0, tlat->abs_period)) {
1843
+
/*
1844
+
* A thread has already set align_next, use it and increment it
1845
+
* to be used by the next thread that wakes up after this one.
1846
+
*/
1847
+
tlat->abs_period = atomic64_add_return_relaxed(
1848
+
osnoise_data.timerlat_align_us * 1000, &align_next);
1849
+
next_abs_period = ns_to_ktime(tlat->abs_period);
1850
+
}
1851
+
1852
+
/*
1849
1853
* If the new abs_period is in the past, skip the activation.
1850
1854
*/
1851
1855
while (ktime_compare(now, next_abs_period) > 0) {
···
2686
2650
.min = &timerlat_min_period,
2687
2651
};
2688
2652
2653
+
/*
2654
+
* osnoise/timerlat_align_us: align the first wakeup of all timerlat
2655
+
* threads to a common boundary (in us). 0 means disabled.
2656
+
*/
2657
+
static struct trace_min_max_param timerlat_align_us = {
2658
+
.lock = &interface_lock,
2659
+
.val = &osnoise_data.timerlat_align_us,
2660
+
.max = NULL,
2661
+
.min = NULL,
2662
+
};
2663
+
2689
2664
static const struct file_operations timerlat_fd_fops = {
2690
2665
.open = timerlat_fd_open,
2691
2666
.read = timerlat_fd_read,
···
2790
2743
2791
2744
tmp = tracefs_create_file("timerlat_period_us", TRACE_MODE_WRITE, top_dir,
2792
2745
&timerlat_period, &trace_min_max_fops);
2746
+
if (!tmp)
2747
+
return -ENOMEM;
2748
+
2749
+
tmp = tracefs_create_file("timerlat_align_us", TRACE_MODE_WRITE, top_dir,
2750
+
&timerlat_align_us, &trace_min_max_fops);
2793
2751
if (!tmp)
2794
2752
return -ENOMEM;
2795
2753