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kyber: add tracepoints

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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 <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Omar Sandoval 2018-09-27 15:55:55 -07:00 committed by Jens Axboe
parent 6e25cb01ea
commit 6c3b7af1c9
2 changed files with 130 additions and 18 deletions
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52
block/kyber-iosched.c
View File

@ -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;
}

96
include/trace/events/kyber.h Normal file
View File

@ -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>