summaryrefslogtreecommitdiff
path: root/kernel/irq/timings.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/irq/timings.c')
-rw-r--r--kernel/irq/timings.c453
1 files changed, 419 insertions, 34 deletions
diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c
index 90c735da15d0..e960d7ce7bcc 100644
--- a/kernel/irq/timings.c
+++ b/kernel/irq/timings.c
@@ -1,10 +1,12 @@
// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2016, Linaro Ltd - Daniel Lezcano <daniel.lezcano@linaro.org>
+#define pr_fmt(fmt) "irq_timings: " fmt
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/static_key.h>
+#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/idr.h>
#include <linux/irq.h>
@@ -261,12 +263,29 @@ void irq_timings_disable(void)
#define EMA_ALPHA_VAL 64
#define EMA_ALPHA_SHIFT 7
-#define PREDICTION_PERIOD_MIN 2
+#define PREDICTION_PERIOD_MIN 3
#define PREDICTION_PERIOD_MAX 5
#define PREDICTION_FACTOR 4
#define PREDICTION_MAX 10 /* 2 ^ PREDICTION_MAX useconds */
#define PREDICTION_BUFFER_SIZE 16 /* slots for EMAs, hardly more than 16 */
+/*
+ * Number of elements in the circular buffer: If it happens it was
+ * flushed before, then the number of elements could be smaller than
+ * IRQ_TIMINGS_SIZE, so the count is used, otherwise the array size is
+ * used as we wrapped. The index begins from zero when we did not
+ * wrap. That could be done in a nicer way with the proper circular
+ * array structure type but with the cost of extra computation in the
+ * interrupt handler hot path. We choose efficiency.
+ */
+#define for_each_irqts(i, irqts) \
+ for (i = irqts->count < IRQ_TIMINGS_SIZE ? \
+ 0 : irqts->count & IRQ_TIMINGS_MASK, \
+ irqts->count = min(IRQ_TIMINGS_SIZE, \
+ irqts->count); \
+ irqts->count > 0; irqts->count--, \
+ i = (i + 1) & IRQ_TIMINGS_MASK)
+
struct irqt_stat {
u64 last_ts;
u64 ema_time[PREDICTION_BUFFER_SIZE];
@@ -297,7 +316,16 @@ static u64 irq_timings_ema_new(u64 value, u64 ema_old)
static int irq_timings_next_event_index(int *buffer, size_t len, int period_max)
{
- int i;
+ int period;
+
+ /*
+ * Move the beginning pointer to the end minus the max period x 3.
+ * We are at the point we can begin searching the pattern
+ */
+ buffer = &buffer[len - (period_max * 3)];
+
+ /* Adjust the length to the maximum allowed period x 3 */
+ len = period_max * 3;
/*
* The buffer contains the suite of intervals, in a ilog2
@@ -306,21 +334,45 @@ static int irq_timings_next_event_index(int *buffer, size_t len, int period_max)
* period beginning at the end of the buffer. We do that for
* each suffix.
*/
- for (i = period_max; i >= PREDICTION_PERIOD_MIN ; i--) {
+ for (period = period_max; period >= PREDICTION_PERIOD_MIN; period--) {
- int *begin = &buffer[len - (i * 3)];
- int *ptr = begin;
+ /*
+ * The first comparison always succeed because the
+ * suffix is deduced from the first n-period bytes of
+ * the buffer and we compare the initial suffix with
+ * itself, so we can skip the first iteration.
+ */
+ int idx = period;
+ size_t size = period;
/*
* We look if the suite with period 'i' repeat
* itself. If it is truncated at the end, as it
* repeats we can use the period to find out the next
- * element.
+ * element with the modulo.
*/
- while (!memcmp(ptr, begin, i * sizeof(*ptr))) {
- ptr += i;
- if (ptr >= &buffer[len])
- return begin[((i * 3) % i)];
+ while (!memcmp(buffer, &buffer[idx], size * sizeof(int))) {
+
+ /*
+ * Move the index in a period basis
+ */
+ idx += size;
+
+ /*
+ * If this condition is reached, all previous
+ * memcmp were successful, so the period is
+ * found.
+ */
+ if (idx == len)
+ return buffer[len % period];
+
+ /*
+ * If the remaining elements to compare are
+ * smaller than the period, readjust the size
+ * of the comparison for the last iteration.
+ */
+ if (len - idx < period)
+ size = len - idx;
}
}
@@ -380,11 +432,43 @@ static u64 __irq_timings_next_event(struct irqt_stat *irqs, int irq, u64 now)
return irqs->last_ts + irqs->ema_time[index];
}
+static __always_inline int irq_timings_interval_index(u64 interval)
+{
+ /*
+ * The PREDICTION_FACTOR increase the interval size for the
+ * array of exponential average.
+ */
+ u64 interval_us = (interval >> 10) / PREDICTION_FACTOR;
+
+ return likely(interval_us) ? ilog2(interval_us) : 0;
+}
+
+static __always_inline void __irq_timings_store(int irq, struct irqt_stat *irqs,
+ u64 interval)
+{
+ int index;
+
+ /*
+ * Get the index in the ema table for this interrupt.
+ */
+ index = irq_timings_interval_index(interval);
+
+ /*
+ * Store the index as an element of the pattern in another
+ * circular array.
+ */
+ irqs->circ_timings[irqs->count & IRQ_TIMINGS_MASK] = index;
+
+ irqs->ema_time[index] = irq_timings_ema_new(interval,
+ irqs->ema_time[index]);
+
+ irqs->count++;
+}
+
static inline void irq_timings_store(int irq, struct irqt_stat *irqs, u64 ts)
{
u64 old_ts = irqs->last_ts;
u64 interval;
- int index;
/*
* The timestamps are absolute time values, we need to compute
@@ -415,24 +499,7 @@ static inline void irq_timings_store(int irq, struct irqt_stat *irqs, u64 ts)
return;
}
- /*
- * Get the index in the ema table for this interrupt. The
- * PREDICTION_FACTOR increase the interval size for the array
- * of exponential average.
- */
- index = likely(interval) ?
- ilog2((interval >> 10) / PREDICTION_FACTOR) : 0;
-
- /*
- * Store the index as an element of the pattern in another
- * circular array.
- */
- irqs->circ_timings[irqs->count & IRQ_TIMINGS_MASK] = index;
-
- irqs->ema_time[index] = irq_timings_ema_new(interval,
- irqs->ema_time[index]);
-
- irqs->count++;
+ __irq_timings_store(irq, irqs, interval);
}
/**
@@ -493,11 +560,7 @@ u64 irq_timings_next_event(u64 now)
* model while decrementing the counter because we consume the
* data from our circular buffer.
*/
-
- i = (irqts->count & IRQ_TIMINGS_MASK) - 1;
- irqts->count = min(IRQ_TIMINGS_SIZE, irqts->count);
-
- for (; irqts->count > 0; irqts->count--, i = (i + 1) & IRQ_TIMINGS_MASK) {
+ for_each_irqts(i, irqts) {
irq = irq_timing_decode(irqts->values[i], &ts);
s = idr_find(&irqt_stats, irq);
if (s)
@@ -564,3 +627,325 @@ int irq_timings_alloc(int irq)
return 0;
}
+
+#ifdef CONFIG_TEST_IRQ_TIMINGS
+struct timings_intervals {
+ u64 *intervals;
+ size_t count;
+};
+
+/*
+ * Intervals are given in nanosecond base
+ */
+static u64 intervals0[] __initdata = {
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000, 500000,
+ 10000, 50000, 200000,
+};
+
+static u64 intervals1[] __initdata = {
+ 223947000, 1240000, 1384000, 1386000, 1386000,
+ 217416000, 1236000, 1384000, 1386000, 1387000,
+ 214719000, 1241000, 1386000, 1387000, 1384000,
+ 213696000, 1234000, 1384000, 1386000, 1388000,
+ 219904000, 1240000, 1385000, 1389000, 1385000,
+ 212240000, 1240000, 1386000, 1386000, 1386000,
+ 214415000, 1236000, 1384000, 1386000, 1387000,
+ 214276000, 1234000,
+};
+
+static u64 intervals2[] __initdata = {
+ 4000, 3000, 5000, 100000,
+ 3000, 3000, 5000, 117000,
+ 4000, 4000, 5000, 112000,
+ 4000, 3000, 4000, 110000,
+ 3000, 5000, 3000, 117000,
+ 4000, 4000, 5000, 112000,
+ 4000, 3000, 4000, 110000,
+ 3000, 4000, 5000, 112000,
+ 4000,
+};
+
+static u64 intervals3[] __initdata = {
+ 1385000, 212240000, 1240000,
+ 1386000, 214415000, 1236000,
+ 1384000, 214276000, 1234000,
+ 1386000, 214415000, 1236000,
+ 1385000, 212240000, 1240000,
+ 1386000, 214415000, 1236000,
+ 1384000, 214276000, 1234000,
+ 1386000, 214415000, 1236000,
+ 1385000, 212240000, 1240000,
+};
+
+static u64 intervals4[] __initdata = {
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000, 50000, 10000, 50000,
+ 10000,
+};
+
+static struct timings_intervals tis[] __initdata = {
+ { intervals0, ARRAY_SIZE(intervals0) },
+ { intervals1, ARRAY_SIZE(intervals1) },
+ { intervals2, ARRAY_SIZE(intervals2) },
+ { intervals3, ARRAY_SIZE(intervals3) },
+ { intervals4, ARRAY_SIZE(intervals4) },
+};
+
+static int __init irq_timings_test_next_index(struct timings_intervals *ti)
+{
+ int _buffer[IRQ_TIMINGS_SIZE];
+ int buffer[IRQ_TIMINGS_SIZE];
+ int index, start, i, count, period_max;
+
+ count = ti->count - 1;
+
+ period_max = count > (3 * PREDICTION_PERIOD_MAX) ?
+ PREDICTION_PERIOD_MAX : count / 3;
+
+ /*
+ * Inject all values except the last one which will be used
+ * to compare with the next index result.
+ */
+ pr_debug("index suite: ");
+
+ for (i = 0; i < count; i++) {
+ index = irq_timings_interval_index(ti->intervals[i]);
+ _buffer[i & IRQ_TIMINGS_MASK] = index;
+ pr_cont("%d ", index);
+ }
+
+ start = count < IRQ_TIMINGS_SIZE ? 0 :
+ count & IRQ_TIMINGS_MASK;
+
+ count = min_t(int, count, IRQ_TIMINGS_SIZE);
+
+ for (i = 0; i < count; i++) {
+ int index = (start + i) & IRQ_TIMINGS_MASK;
+ buffer[i] = _buffer[index];
+ }
+
+ index = irq_timings_next_event_index(buffer, count, period_max);
+ i = irq_timings_interval_index(ti->intervals[ti->count - 1]);
+
+ if (index != i) {
+ pr_err("Expected (%d) and computed (%d) next indexes differ\n",
+ i, index);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int __init irq_timings_next_index_selftest(void)
+{
+ int i, ret;
+
+ for (i = 0; i < ARRAY_SIZE(tis); i++) {
+
+ pr_info("---> Injecting intervals number #%d (count=%zd)\n",
+ i, tis[i].count);
+
+ ret = irq_timings_test_next_index(&tis[i]);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int __init irq_timings_test_irqs(struct timings_intervals *ti)
+{
+ struct irqt_stat __percpu *s;
+ struct irqt_stat *irqs;
+ int i, index, ret, irq = 0xACE5;
+
+ ret = irq_timings_alloc(irq);
+ if (ret) {
+ pr_err("Failed to allocate irq timings\n");
+ return ret;
+ }
+
+ s = idr_find(&irqt_stats, irq);
+ if (!s) {
+ ret = -EIDRM;
+ goto out;
+ }
+
+ irqs = this_cpu_ptr(s);
+
+ for (i = 0; i < ti->count; i++) {
+
+ index = irq_timings_interval_index(ti->intervals[i]);
+ pr_debug("%d: interval=%llu ema_index=%d\n",
+ i, ti->intervals[i], index);
+
+ __irq_timings_store(irq, irqs, ti->intervals[i]);
+ if (irqs->circ_timings[i & IRQ_TIMINGS_MASK] != index) {
+ pr_err("Failed to store in the circular buffer\n");
+ goto out;
+ }
+ }
+
+ if (irqs->count != ti->count) {
+ pr_err("Count differs\n");
+ goto out;
+ }
+
+ ret = 0;
+out:
+ irq_timings_free(irq);
+
+ return ret;
+}
+
+static int __init irq_timings_irqs_selftest(void)
+{
+ int i, ret;
+
+ for (i = 0; i < ARRAY_SIZE(tis); i++) {
+ pr_info("---> Injecting intervals number #%d (count=%zd)\n",
+ i, tis[i].count);
+ ret = irq_timings_test_irqs(&tis[i]);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int __init irq_timings_test_irqts(struct irq_timings *irqts,
+ unsigned count)
+{
+ int start = count >= IRQ_TIMINGS_SIZE ? count - IRQ_TIMINGS_SIZE : 0;
+ int i, irq, oirq = 0xBEEF;
+ u64 ots = 0xDEAD, ts;
+
+ /*
+ * Fill the circular buffer by using the dedicated function.
+ */
+ for (i = 0; i < count; i++) {
+ pr_debug("%d: index=%d, ts=%llX irq=%X\n",
+ i, i & IRQ_TIMINGS_MASK, ots + i, oirq + i);
+
+ irq_timings_push(ots + i, oirq + i);
+ }
+
+ /*
+ * Compute the first elements values after the index wrapped
+ * up or not.
+ */
+ ots += start;
+ oirq += start;
+
+ /*
+ * Test the circular buffer count is correct.
+ */
+ pr_debug("---> Checking timings array count (%d) is right\n", count);
+ if (WARN_ON(irqts->count != count))
+ return -EINVAL;
+
+ /*
+ * Test the macro allowing to browse all the irqts.
+ */
+ pr_debug("---> Checking the for_each_irqts() macro\n");
+ for_each_irqts(i, irqts) {
+
+ irq = irq_timing_decode(irqts->values[i], &ts);
+
+ pr_debug("index=%d, ts=%llX / %llX, irq=%X / %X\n",
+ i, ts, ots, irq, oirq);
+
+ if (WARN_ON(ts != ots || irq != oirq))
+ return -EINVAL;
+
+ ots++; oirq++;
+ }
+
+ /*
+ * The circular buffer should have be flushed when browsed
+ * with for_each_irqts
+ */
+ pr_debug("---> Checking timings array is empty after browsing it\n");
+ if (WARN_ON(irqts->count))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int __init irq_timings_irqts_selftest(void)
+{
+ struct irq_timings *irqts = this_cpu_ptr(&irq_timings);
+ int i, ret;
+
+ /*
+ * Test the circular buffer with different number of
+ * elements. The purpose is to test at the limits (empty, half
+ * full, full, wrapped with the cursor at the boundaries,
+ * wrapped several times, etc ...
+ */
+ int count[] = { 0,
+ IRQ_TIMINGS_SIZE >> 1,
+ IRQ_TIMINGS_SIZE,
+ IRQ_TIMINGS_SIZE + (IRQ_TIMINGS_SIZE >> 1),
+ 2 * IRQ_TIMINGS_SIZE,
+ (2 * IRQ_TIMINGS_SIZE) + 3,
+ };
+
+ for (i = 0; i < ARRAY_SIZE(count); i++) {
+
+ pr_info("---> Checking the timings with %d/%d values\n",
+ count[i], IRQ_TIMINGS_SIZE);
+
+ ret = irq_timings_test_irqts(irqts, count[i]);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static int __init irq_timings_selftest(void)
+{
+ int ret;
+
+ pr_info("------------------- selftest start -----------------\n");
+
+ /*
+ * At this point, we don't except any subsystem to use the irq
+ * timings but us, so it should not be enabled.
+ */
+ if (static_branch_unlikely(&irq_timing_enabled)) {
+ pr_warn("irq timings already initialized, skipping selftest\n");
+ return 0;
+ }
+
+ ret = irq_timings_irqts_selftest();
+ if (ret)
+ goto out;
+
+ ret = irq_timings_irqs_selftest();
+ if (ret)
+ goto out;
+
+ ret = irq_timings_next_index_selftest();
+out:
+ pr_info("---------- selftest end with %s -----------\n",
+ ret ? "failure" : "success");
+
+ return ret;
+}
+early_initcall(irq_timings_selftest);
+#endif
generated by cgit v1.2.3-70-g09d2 (git 2.47.1) at 2024-12-29 14:00:04 +0000