From: Omar Sandoval <osan...@fb.com>
When debugging Kyber, it's really useful to know what latencies we've
been having, how the domain depths have been adjusted, and if we've
actually been throttling. Add three tracepoints, kyber_latency,
kyber_adjust, and kyber_throttled, to record that.
Signed-off-by: Omar Sandoval <osan...@fb.com>
---
block/kyber-iosched.c | 52 ++++++++++++-------
include/trace/events/kyber.h | 96 ++++++++++++++++++++++++++++++++++++
2 files changed, 130 insertions(+), 18 deletions(-)
create mode 100644 include/trace/events/kyber.h
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index adc8e6393829..2b62e362fb36 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -30,6 +30,9 @@
#include "blk-mq-sched.h"
#include "blk-mq-tag.h"
+#define CREATE_TRACE_POINTS
+#include <trace/events/kyber.h>
+
/*
* Scheduling domains: the device is divided into multiple domains based on the
* request type.
@@ -42,6 +45,13 @@ enum {
KYBER_NUM_DOMAINS,
};
+static const char *kyber_domain_names[] = {
+ [KYBER_READ] = "READ",
+ [KYBER_WRITE] = "WRITE",
+ [KYBER_DISCARD] = "DISCARD",
+ [KYBER_OTHER] = "OTHER",
+};
+
enum {
/*
* In order to prevent starvation of synchronous requests by a flood of
@@ -122,6 +132,11 @@ enum {
KYBER_IO_LATENCY,
};
+static const char *kyber_latency_type_names[] = {
+ [KYBER_TOTAL_LATENCY] = "total",
+ [KYBER_IO_LATENCY] = "I/O",
+};
+
/*
* Per-cpu latency histograms: total latency and I/O latency for each
scheduling
* domain except for KYBER_OTHER.
@@ -144,6 +159,8 @@ struct kyber_ctx_queue {
} ____cacheline_aligned_in_smp;
struct kyber_queue_data {
+ struct request_queue *q;
+
/*
* Each scheduling domain has a limited number of in-flight requests
* device-wide, limited by these tokens.
@@ -249,6 +266,10 @@ static int calculate_percentile(struct kyber_queue_data
*kqd,
}
memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
+ trace_kyber_latency(kqd->q, kyber_domain_names[sched_domain],
+ kyber_latency_type_names[type], percentile,
+ bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
+
return bucket;
}
@@ -256,8 +277,11 @@ static void kyber_resize_domain(struct kyber_queue_data
*kqd,
unsigned int sched_domain, unsigned int depth)
{
depth = clamp(depth, 1U, kyber_depth[sched_domain]);
- if (depth != kqd->domain_tokens[sched_domain].sb.depth)
+ if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
+ trace_kyber_adjust(kqd->q, kyber_domain_names[sched_domain],
+ depth);
+ }
}
static void kyber_timer_fn(struct timer_list *t)
@@ -360,6 +384,8 @@ static struct kyber_queue_data
*kyber_queue_data_alloc(struct request_queue *q)
if (!kqd)
goto err;
+ kqd->q = q;
+
kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
GFP_KERNEL | __GFP_ZERO);
if (!kqd->cpu_latency)
@@ -756,6 +782,9 @@ kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
rq_set_domain_token(rq, nr);
list_del_init(&rq->queuelist);
return rq;
+ } else {
+ trace_kyber_throttled(kqd->q,
+
kyber_domain_names[khd->cur_domain]);
}
} else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
nr = kyber_get_domain_token(kqd, khd, hctx);
@@ -766,6 +795,9 @@ kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
rq_set_domain_token(rq, nr);
list_del_init(&rq->queuelist);
return rq;
+ } else {
+ trace_kyber_throttled(kqd->q,
+
kyber_domain_names[khd->cur_domain]);
}
}
@@ -944,23 +976,7 @@ static int kyber_cur_domain_show(void *data, struct
seq_file *m)
struct blk_mq_hw_ctx *hctx = data;
struct kyber_hctx_data *khd = hctx->sched_data;
- switch (khd->cur_domain) {
- case KYBER_READ:
- seq_puts(m, "READ\n");
- break;
- case KYBER_WRITE:
- seq_puts(m, "WRITE\n");
- break;
- case KYBER_DISCARD:
- seq_puts(m, "DISCARD\n");
- break;
- case KYBER_OTHER:
- seq_puts(m, "OTHER\n");
- break;
- default:
- seq_printf(m, "%u\n", khd->cur_domain);
- break;
- }
+ seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
return 0;
}
diff --git a/include/trace/events/kyber.h b/include/trace/events/kyber.h
new file mode 100644
index 000000000000..a9834c37ac40
--- /dev/null
+++ b/include/trace/events/kyber.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM kyber
+
+#if !defined(_TRACE_KYBER_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_KYBER_H
+
+#include <linux/blkdev.h>
+#include <linux/tracepoint.h>
+
+#define DOMAIN_LEN 16
+#define LATENCY_TYPE_LEN 8
+
+TRACE_EVENT(kyber_latency,
+
+ TP_PROTO(struct request_queue *q, const char *domain, const char *type,
+ unsigned int percentile, unsigned int numerator,
+ unsigned int denominator, unsigned int samples),
+
+ TP_ARGS(q, domain, type, percentile, numerator, denominator, samples),
+
+ TP_STRUCT__entry(
+ __field( dev_t, dev )
+ __array( char, domain, DOMAIN_LEN )
+ __array( char, type, LATENCY_TYPE_LEN )
+ __field( u8, percentile )
+ __field( u8, numerator )
+ __field( u8, denominator )
+ __field( unsigned int, samples )
+ ),
+
+ TP_fast_assign(
+ __entry->dev =
disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+ strlcpy(__entry->domain, domain, DOMAIN_LEN);
+ strlcpy(__entry->type, type, DOMAIN_LEN);
+ __entry->percentile = percentile;
+ __entry->numerator = numerator;
+ __entry->denominator = denominator;
+ __entry->samples = samples;
+ ),
+
+ TP_printk("%d,%d %s %s p%u %u/%u samples=%u",
+ MAJOR(__entry->dev), MINOR(__entry->dev), __entry->domain,
+ __entry->type, __entry->percentile, __entry->numerator,
+ __entry->denominator, __entry->samples)
+);
+
+TRACE_EVENT(kyber_adjust,
+
+ TP_PROTO(struct request_queue *q, const char *domain,
+ unsigned int depth),
+
+ TP_ARGS(q, domain, depth),
+
+ TP_STRUCT__entry(
+ __field( dev_t, dev )
+ __array( char, domain, DOMAIN_LEN )
+ __field( unsigned int, depth )
+ ),
+
+ TP_fast_assign(
+ __entry->dev =
disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+ strlcpy(__entry->domain, domain, DOMAIN_LEN);
+ __entry->depth = depth;
+ ),
+
+ TP_printk("%d,%d %s %u",
+ MAJOR(__entry->dev), MINOR(__entry->dev), __entry->domain,
+ __entry->depth)
+);
+
+TRACE_EVENT(kyber_throttled,
+
+ TP_PROTO(struct request_queue *q, const char *domain),
+
+ TP_ARGS(q, domain),
+
+ TP_STRUCT__entry(
+ __field( dev_t, dev )
+ __array( char, domain, DOMAIN_LEN )
+ ),
+
+ TP_fast_assign(
+ __entry->dev =
disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+ strlcpy(__entry->domain, domain, DOMAIN_LEN);
+ ),
+
+ TP_printk("%d,%d %s", MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->domain)
+);
+
+#define _TRACE_KYBER_H
+#endif /* _TRACE_KYBER_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
--
2.19.0
