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examples/tracing: add io_latencies - IO latency distribution monitor
This adds flexible low overhead latency percentile monitoring for block devices which can be useful in understanding and debugging IO related issues. Signed-off-by: Tejun Heo <[email protected]>
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#!/usr/bin/python3 | ||
# | ||
# io_latencies.py Monitor IO latency distribution of a block device. | ||
# | ||
# $ ./io_latencies.py 259:0 | ||
# 259:0 p1 p5 p10 p16 p25 p50 p75 p84 p90 p95 p99 p100 | ||
# read 95us 175us 305us 515us 895us 985us 995us 1.5ms 2.5ms 3.5ms 4.5ms 10ms | ||
# write 5us 5us 5us 15us 25us 135us 765us 855us 885us 895us 965us 1.5ms | ||
# discard 5us 5us 5us 5us 135us 145us 165us 205us 385us 875us 1.5ms 2.5ms | ||
# flush 5us 5us 5us 5us 5us 5us 5us 5us 5us 1.5ms 4.5ms 5.5ms | ||
# | ||
# Copyright (C) 2020 Tejun Heo <[email protected]> | ||
# Copyright (C) 2020 Facebook | ||
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from __future__ import print_function | ||
from bcc import BPF | ||
from time import sleep | ||
import argparse | ||
import json | ||
import sys | ||
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description = """ | ||
Monitor IO latency distribution of a block device | ||
""" | ||
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parser = argparse.ArgumentParser(description = description, | ||
formatter_class = argparse.ArgumentDefaultsHelpFormatter) | ||
parser.add_argument('devno', metavar='MAJ:MIN', type=str, | ||
help='Target block device number') | ||
parser.add_argument('-i', '--interval', type=int, default=3, | ||
help='Report interval') | ||
parser.add_argument('-w', '--which', choices=['from-rq-alloc', 'after-rq-alloc', 'on-device'], | ||
default='on-device', help='Which latency to measure') | ||
parser.add_argument('-p', '--pcts', metavar='PCT', type=float, nargs='+', | ||
default=[1, 5, 10, 16, 25, 50, 75, 84, 90, 95, 99, 100], | ||
help='Percentiles to calculate') | ||
parser.add_argument('-j', '--json', action='store_true', | ||
help='Output in json') | ||
parser.add_argument('--verbose', '-v', action='count', default = 0) | ||
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bpf_source = """ | ||
#include <linux/blk_types.h> | ||
#include <linux/blkdev.h> | ||
#include <linux/time64.h> | ||
BPF_PERCPU_ARRAY(rwdf_100ms, u64, 400); | ||
BPF_PERCPU_ARRAY(rwdf_1ms, u64, 400); | ||
BPF_PERCPU_ARRAY(rwdf_10us, u64, 400); | ||
void kprobe_blk_account_io_done(struct pt_regs *ctx, struct request *rq, u64 now) | ||
{ | ||
unsigned int cmd_flags; | ||
u64 dur; | ||
size_t base, slot; | ||
if (!rq->__START_TIME_FIELD__) | ||
return; | ||
if (!rq->rq_disk || | ||
rq->rq_disk->major != __MAJOR__ || | ||
rq->rq_disk->first_minor != __MINOR__) | ||
return; | ||
cmd_flags = rq->cmd_flags; | ||
switch (cmd_flags & REQ_OP_MASK) { | ||
case REQ_OP_READ: | ||
base = 0; | ||
break; | ||
case REQ_OP_WRITE: | ||
base = 100; | ||
break; | ||
case REQ_OP_DISCARD: | ||
base = 200; | ||
break; | ||
case REQ_OP_FLUSH: | ||
base = 300; | ||
break; | ||
default: | ||
return; | ||
} | ||
dur = now - rq->__START_TIME_FIELD__; | ||
slot = min_t(size_t, div_u64(dur, 100 * NSEC_PER_MSEC), 99); | ||
rwdf_100ms.increment(base + slot); | ||
if (slot) | ||
return; | ||
slot = min_t(size_t, div_u64(dur, NSEC_PER_MSEC), 99); | ||
rwdf_1ms.increment(base + slot); | ||
if (slot) | ||
return; | ||
slot = min_t(size_t, div_u64(dur, 10 * NSEC_PER_USEC), 99); | ||
rwdf_10us.increment(base + slot); | ||
} | ||
""" | ||
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args = parser.parse_args() | ||
args.pcts.sort() | ||
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if args.which == 'from-rq-alloc': | ||
start_time_field = 'alloc_time_ns' | ||
elif args.which == 'after-rq-alloc': | ||
start_time_field = 'start_time_ns' | ||
elif args.which == 'on-device': | ||
start_time_field = 'io_start_time_ns' | ||
else: | ||
die() | ||
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bpf_source = bpf_source.replace('__START_TIME_FIELD__', start_time_field) | ||
bpf_source = bpf_source.replace('__MAJOR__', str(int(args.devno.split(':')[0]))) | ||
bpf_source = bpf_source.replace('__MINOR__', str(int(args.devno.split(':')[1]))) | ||
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bpf = BPF(text=bpf_source) | ||
bpf.attach_kprobe(event="blk_account_io_done", fn_name="kprobe_blk_account_io_done") | ||
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# times are in usecs | ||
MSEC = 1000 | ||
SEC = 1000 * 1000 | ||
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cur_rwdf_100ms = bpf["rwdf_100ms"] | ||
cur_rwdf_1ms = bpf["rwdf_1ms"] | ||
cur_rwdf_10us = bpf["rwdf_10us"] | ||
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last_rwdf_100ms = [0] * 400 | ||
last_rwdf_1ms = [0] * 400 | ||
last_rwdf_10us = [0] * 400 | ||
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rwdf_100ms = [0] * 400 | ||
rwdf_1ms = [0] * 400 | ||
rwdf_10us = [0] * 400 | ||
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io_type = ["read", "write", "discard", "flush"] | ||
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def find_pct(req, total, slots, idx, counted): | ||
while idx > 0: | ||
idx -= 1 | ||
if slots[idx] > 0: | ||
counted += slots[idx] | ||
if args.verbose > 1: | ||
print('idx={} counted={} pct={:.1f} req={}' | ||
.format(idx, counted, counted / total, req)) | ||
if (counted / total) * 100 >= 100 - req: | ||
break | ||
return (idx, counted) | ||
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def calc_lat_pct(req_pcts, total, lat_100ms, lat_1ms, lat_10us): | ||
pcts = [0] * len(req_pcts) | ||
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if total == 0: | ||
return pcts | ||
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data = [(100 * MSEC, lat_100ms), (MSEC, lat_1ms), (10, lat_10us)] | ||
data_sel = 0 | ||
idx = 100 | ||
counted = 0 | ||
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for pct_idx in reversed(range(len(req_pcts))): | ||
req = req_pcts[pct_idx] | ||
while True: | ||
last_counted = counted | ||
(gran, slots) = data[data_sel] | ||
(idx, counted) = find_pct(req, total, slots, idx, counted) | ||
if args.verbose > 1: | ||
print('pct_idx={} req={} gran={} idx={} counted={} total={}' | ||
.format(pct_idx, req, gran, idx, counted, total)) | ||
if idx > 0 or data_sel == len(data) - 1: | ||
break | ||
counted = last_counted | ||
data_sel += 1 | ||
idx = 100 | ||
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pcts[pct_idx] = gran * idx + gran / 2 | ||
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return pcts | ||
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def format_usec(lat): | ||
if lat > SEC: | ||
return '{:.1f}s'.format(lat / SEC) | ||
elif lat > 10 * MSEC: | ||
return '{:.0f}ms'.format(lat / MSEC) | ||
elif lat > MSEC: | ||
return '{:.1f}ms'.format(lat / MSEC) | ||
elif lat > 0: | ||
return '{:.0f}us'.format(lat) | ||
else: | ||
return '-' | ||
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# 0 interval can be used to test whether this script would run successfully. | ||
if args.interval == 0: | ||
sys.exit(0) | ||
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while True: | ||
sleep(args.interval) | ||
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rwdf_total = [0] * 4; | ||
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for i in range(400): | ||
v = cur_rwdf_100ms.sum(i).value | ||
rwdf_100ms[i] = max(v - last_rwdf_100ms[i], 0) | ||
last_rwdf_100ms[i] = v | ||
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v = cur_rwdf_1ms.sum(i).value | ||
rwdf_1ms[i] = max(v - last_rwdf_1ms[i], 0) | ||
last_rwdf_1ms[i] = v | ||
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v = cur_rwdf_10us.sum(i).value | ||
rwdf_10us[i] = max(v - last_rwdf_10us[i], 0) | ||
last_rwdf_10us[i] = v | ||
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rwdf_total[int(i / 100)] += rwdf_100ms[i] | ||
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rwdf_lat = [] | ||
for i in range(4): | ||
left = i * 100 | ||
right = left + 100 | ||
rwdf_lat.append( | ||
calc_lat_pct(args.pcts, rwdf_total[i], | ||
rwdf_100ms[left:right], | ||
rwdf_1ms[left:right], | ||
rwdf_10us[left:right])) | ||
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if args.verbose: | ||
print('{:7} 100ms {}'.format(io_type[i], rwdf_100ms[left:right])) | ||
print('{:7} 1ms {}'.format(io_type[i], rwdf_1ms[left:right])) | ||
print('{:7} 10us {}'.format(io_type[i], rwdf_10us[left:right])) | ||
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if args.json: | ||
result = {} | ||
for iot in range(4): | ||
lats = {} | ||
for pi in range(len(args.pcts)): | ||
lats[args.pcts[pi]] = rwdf_lat[iot][pi] / SEC | ||
result[io_type[iot]] = lats | ||
print(json.dumps(result), flush=True) | ||
else: | ||
print('\n{:<7}'.format(args.devno), end='') | ||
widths = [] | ||
for pct in args.pcts: | ||
pct_str = 'p{:g}'.format(pct) | ||
widths.append(max(len(pct_str), 5)) | ||
print(' {:>5}'.format(pct_str), end='') | ||
print() | ||
for iot in range(4): | ||
print('{:7}'.format(io_type[iot]), end='') | ||
for pi in range(len(rwdf_lat[iot])): | ||
print(' {:>{}}'.format(format_usec(rwdf_lat[iot][pi]), widths[pi]), end='') | ||
print() |