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#! /usr/bin/python3
#
# biolatpcts.py Monitor IO latency distribution of a block device.
#
# $ ./biolatpcts.py /dev/nvme0n1
# nvme0n1 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 <tj@kernel.org>
# Copyright (C) 2020 Facebook
from __future__ import print_function
from bcc import BPF
from time import sleep
from threading import Event
import argparse
import json
import sys
import os
import signal
description = """
Monitor IO latency distribution of a block device
"""
epilog = """
When interval is infinite, biolatpcts will print out result once the
initialization is complete to indicate readiness. After initialized,
biolatpcts will output whenever it receives SIGUSR1/2 and before exiting on
SIGINT, SIGTERM or SIGHUP.
SIGUSR1 starts a new period after reporting. SIGUSR2 doesn't and can be used
to monitor progress without affecting accumulation of data points. They can
be used to obtain latency distribution between two arbitrary events and
monitor progress inbetween.
"""
parser = argparse.ArgumentParser(description = description, epilog = epilog,
formatter_class = argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('dev', metavar='DEV', type=str,
help='Target block device (/dev/DEVNAME, DEVNAME or MAJ:MIN)')
parser.add_argument('-i', '--interval', type=int, default=3,
help='Report interval (0: exit after startup, -1: infinite)')
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=str,
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)
bpf_source = """
#include <linux/blk_types.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.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);
RAW_TRACEPOINT_PROBE(block_rq_complete)
{
// TP_PROTO(struct request *rq, blk_status_t error, unsigned int nr_bytes)
struct request *rq = (void *)ctx->args[0];
unsigned int cmd_flags;
u64 dur;
size_t base, slot;
if (!rq->__START_TIME_FIELD__)
return 0;
if (!rq->__RQ_DISK__ ||
rq->__RQ_DISK__->major != __MAJOR__ ||
rq->__RQ_DISK__->first_minor != __MINOR__)
return 0;
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 0;
}
dur = bpf_ktime_get_ns() - 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 0;
slot = min_t(size_t, div_u64(dur, NSEC_PER_MSEC), 99);
rwdf_1ms.increment(base + slot);
if (slot)
return 0;
slot = min_t(size_t, div_u64(dur, 10 * NSEC_PER_USEC), 99);
rwdf_10us.increment(base + slot);
return 0;
}
"""
args = parser.parse_args()
args.pcts = args.pcts.split(',')
args.pcts.sort(key=lambda x: float(x))
try:
major = int(args.dev.split(':')[0])
minor = int(args.dev.split(':')[1])
except Exception:
if '/' in args.dev:
stat = os.stat(args.dev)
else:
stat = os.stat('/dev/' + args.dev)
major = os.major(stat.st_rdev)
minor = os.minor(stat.st_rdev)
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:
print("Invalid latency measurement {}".format(args.which))
exit()
bpf_source = bpf_source.replace('__START_TIME_FIELD__', start_time_field)
bpf_source = bpf_source.replace('__MAJOR__', str(major))
bpf_source = bpf_source.replace('__MINOR__', str(minor))
if BPF.kernel_struct_has_field(b'request', b'rq_disk') == 1:
bpf_source = bpf_source.replace('__RQ_DISK__', 'rq_disk')
else:
bpf_source = bpf_source.replace('__RQ_DISK__', 'q->disk')
bpf = BPF(text=bpf_source)
# times are in usecs
MSEC = 1000
SEC = 1000 * 1000
cur_rwdf_100ms = bpf["rwdf_100ms"]
cur_rwdf_1ms = bpf["rwdf_1ms"]
cur_rwdf_10us = bpf["rwdf_10us"]
last_rwdf_100ms = [0] * 400
last_rwdf_1ms = [0] * 400
last_rwdf_10us = [0] * 400
rwdf_100ms = [0] * 400
rwdf_1ms = [0] * 400
rwdf_10us = [0] * 400
io_type = ["read", "write", "discard", "flush"]
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)
def calc_lat_pct(req_pcts, total, lat_100ms, lat_1ms, lat_10us):
pcts = [0] * len(req_pcts)
if total == 0:
return pcts
data = [(100 * MSEC, lat_100ms), (MSEC, lat_1ms), (10, lat_10us)]
data_sel = 0
idx = 100
counted = 0
for pct_idx in reversed(range(len(req_pcts))):
req = float(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
pcts[pct_idx] = gran * idx + gran / 2
return pcts
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 '-'
# 0 interval can be used to test whether this script would run successfully.
if args.interval == 0:
sys.exit(0)
# Set up signal handling so that we print the result on USR1/2 and before
# exiting on a signal. Combined with infinite interval, this can be used to
# obtain overall latency distribution between two events. On USR2 the
# accumulated counters are cleared too, which can be used to define
# arbitrary intervals.
force_update_last_rwdf = False
keep_running = True
result_req = Event()
def sig_handler(sig, frame):
global keep_running, force_update_last_rwdf, result_req
if sig == signal.SIGUSR1:
force_update_last_rwdf = True
elif sig != signal.SIGUSR2:
keep_running = False
result_req.set()
for sig in (signal.SIGUSR1, signal.SIGUSR2, signal.SIGINT, signal.SIGTERM, signal.SIGHUP):
signal.signal(sig, sig_handler)
# If infinite interval, always trigger the first output so that the caller
# can tell when initialization is complete.
if args.interval < 0:
result_req.set();
while keep_running:
result_req.wait(args.interval if args.interval > 0 else None)
result_req.clear()
update_last_rwdf = args.interval > 0 or force_update_last_rwdf
force_update_last_rwdf = False
rwdf_total = [0] * 4;
for i in range(400):
v = cur_rwdf_100ms.sum(i).value
rwdf_100ms[i] = max(v - last_rwdf_100ms[i], 0)
if update_last_rwdf:
last_rwdf_100ms[i] = v
v = cur_rwdf_1ms.sum(i).value
rwdf_1ms[i] = max(v - last_rwdf_1ms[i], 0)
if update_last_rwdf:
last_rwdf_1ms[i] = v
v = cur_rwdf_10us.sum(i).value
rwdf_10us[i] = max(v - last_rwdf_10us[i], 0)
if update_last_rwdf:
last_rwdf_10us[i] = v
rwdf_total[int(i / 100)] += rwdf_100ms[i]
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]))
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]))
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(os.path.basename(args.dev)), end='')
widths = []
for pct in args.pcts:
widths.append(max(len(pct), 5))
print(' {:>5}'.format(pct), 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()
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