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#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# biolatency Summarize block device I/O latency as a histogram.
# For Linux, uses BCC, eBPF.
#
# USAGE: biolatency [-h] [-T] [-Q] [-m] [-D] [interval] [count]
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 20-Sep-2015 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse
# arguments
examples = """examples:
./biolatency # summarize block I/O latency as a histogram
./biolatency 1 10 # print 1 second summaries, 10 times
./biolatency -mT 1 # 1s summaries, milliseconds, and timestamps
./biolatency -Q # include OS queued time in I/O time
./biolatency -D # show each disk device separately
./biolatency -F # show I/O flags separately
"""
parser = argparse.ArgumentParser(
description="Summarize block device I/O latency as a histogram",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-T", "--timestamp", action="store_true",
help="include timestamp on output")
parser.add_argument("-Q", "--queued", action="store_true",
help="include OS queued time in I/O time")
parser.add_argument("-m", "--milliseconds", action="store_true",
help="millisecond histogram")
parser.add_argument("-D", "--disks", action="store_true",
help="print a histogram per disk device")
parser.add_argument("-F", "--flags", action="store_true",
help="print a histogram per set of I/O flags")
parser.add_argument("interval", nargs="?", default=99999999,
help="output interval, in seconds")
parser.add_argument("count", nargs="?", default=99999999,
help="number of outputs")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
countdown = int(args.count)
debug = 0
if args.flags and args.disks:
print("ERROR: can only use -D or -F. Exiting.")
exit()
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>
typedef struct disk_key {
char disk[DISK_NAME_LEN];
u64 slot;
} disk_key_t;
typedef struct flag_key {
u64 flags;
u64 slot;
} flag_key_t;
BPF_HASH(start, struct request *);
STORAGE
// time block I/O
int trace_req_start(struct pt_regs *ctx, struct request *req)
{
u64 ts = bpf_ktime_get_ns();
start.update(&req, &ts);
return 0;
}
// output
int trace_req_done(struct pt_regs *ctx, struct request *req)
{
u64 *tsp, delta;
// fetch timestamp and calculate delta
tsp = start.lookup(&req);
if (tsp == 0) {
return 0; // missed issue
}
delta = bpf_ktime_get_ns() - *tsp;
FACTOR
// store as histogram
STORE
start.delete(&req);
return 0;
}
"""
# code substitutions
if args.milliseconds:
bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000000;')
label = "msecs"
else:
bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000;')
label = "usecs"
if args.disks:
bpf_text = bpf_text.replace('STORAGE',
'BPF_HISTOGRAM(dist, disk_key_t);')
bpf_text = bpf_text.replace('STORE',
'disk_key_t key = {.slot = bpf_log2l(delta)}; ' +
'void *__tmp = (void *)req->rq_disk->disk_name; ' +
'bpf_probe_read(&key.disk, sizeof(key.disk), __tmp); ' +
'dist.increment(key);')
elif args.flags:
bpf_text = bpf_text.replace('STORAGE',
'BPF_HISTOGRAM(dist, flag_key_t);')
bpf_text = bpf_text.replace('STORE',
'flag_key_t key = {.slot = bpf_log2l(delta)}; ' +
'key.flags = req->cmd_flags; ' +
'dist.increment(key);')
else:
bpf_text = bpf_text.replace('STORAGE', 'BPF_HISTOGRAM(dist);')
bpf_text = bpf_text.replace('STORE',
'dist.increment(bpf_log2l(delta));')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# load BPF program
b = BPF(text=bpf_text)
if args.queued:
b.attach_kprobe(event="blk_account_io_start", fn_name="trace_req_start")
else:
if BPF.get_kprobe_functions(b'blk_start_request'):
b.attach_kprobe(event="blk_start_request", fn_name="trace_req_start")
b.attach_kprobe(event="blk_mq_start_request", fn_name="trace_req_start")
b.attach_kprobe(event="blk_account_io_done",
fn_name="trace_req_done")
print("Tracing block device I/O... Hit Ctrl-C to end.")
# see blk_fill_rwbs():
req_opf = {
0: "Read",
1: "Write",
2: "Flush",
3: "Discard",
5: "SecureErase",
6: "ZoneReset",
7: "WriteSame",
9: "WriteZeros"
}
REQ_OP_BITS = 8
REQ_OP_MASK = ((1 << REQ_OP_BITS) - 1)
REQ_SYNC = 1 << (REQ_OP_BITS + 3)
REQ_META = 1 << (REQ_OP_BITS + 4)
REQ_PRIO = 1 << (REQ_OP_BITS + 5)
REQ_NOMERGE = 1 << (REQ_OP_BITS + 6)
REQ_IDLE = 1 << (REQ_OP_BITS + 7)
REQ_FUA = 1 << (REQ_OP_BITS + 9)
REQ_RAHEAD = 1 << (REQ_OP_BITS + 11)
REQ_BACKGROUND = 1 << (REQ_OP_BITS + 12)
REQ_NOWAIT = 1 << (REQ_OP_BITS + 13)
def flags_print(flags):
desc = ""
# operation
if flags & REQ_OP_MASK in req_opf:
desc = req_opf[flags & REQ_OP_MASK]
else:
desc = "Unknown"
# flags
if flags & REQ_SYNC:
desc = "Sync-" + desc
if flags & REQ_META:
desc = "Metadata-" + desc
if flags & REQ_FUA:
desc = "ForcedUnitAccess-" + desc
if flags & REQ_PRIO:
desc = "Priority-" + desc
if flags & REQ_NOMERGE:
desc = "NoMerge-" + desc
if flags & REQ_IDLE:
desc = "Idle-" + desc
if flags & REQ_RAHEAD:
desc = "ReadAhead-" + desc
if flags & REQ_BACKGROUND:
desc = "Background-" + desc
if flags & REQ_NOWAIT:
desc = "NoWait-" + desc
return desc
# output
exiting = 0 if args.interval else 1
dist = b.get_table("dist")
while (1):
try:
sleep(int(args.interval))
except KeyboardInterrupt:
exiting = 1
print()
if args.timestamp:
print("%-8s\n" % strftime("%H:%M:%S"), end="")
if args.flags:
dist.print_log2_hist(label, "flags", flags_print)
else:
dist.print_log2_hist(label, "disk")
dist.clear()
countdown -= 1
if exiting or countdown == 0:
exit()
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