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#! /usr/bin/python3
# @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] [-F] [-e] [-j] [-d DISK] [interval] [count]
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 20-Sep-2015 Brendan Gregg Created this.
# 31-Mar-2022 Rocky Xing Added disk filter support.
# 01-Aug-2023 Jerome Marchand Added support for block tracepoints
from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse
import ctypes as ct
import os
# 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
./biolatency -j # print a dictionary
./biolatency -e # show extension summary(total, average)
./biolatency -d sdc # Trace sdc only
"""
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("-e", "--extension", action="store_true",
help="summarize average/total value")
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)
parser.add_argument("-j", "--json", action="store_true",
help="json output")
parser.add_argument("-d", "--disk", type=str,
help="Trace this disk only")
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/blk-mq.h>
typedef struct disk_key {
dev_t dev;
u64 slot;
} disk_key_t;
typedef struct flag_key {
u64 flags;
u64 slot;
} flag_key_t;
typedef struct ext_val {
u64 total;
u64 count;
} ext_val_t;
struct tp_args {
u64 __unused__;
dev_t dev;
sector_t sector;
unsigned int nr_sector;
unsigned int bytes;
char rwbs[8];
char comm[16];
char cmd[];
};
struct start_key {
dev_t dev;
u32 _pad;
sector_t sector;
CMD_FLAGS
};
BPF_HASH(start, struct start_key);
STORAGE
static dev_t ddevt(struct gendisk *disk) {
return (disk->major << 20) | disk->first_minor;
}
// time block I/O
static int __trace_req_start(struct start_key key)
{
DISK_FILTER
u64 ts = bpf_ktime_get_ns();
start.update(&key, &ts);
return 0;
}
int trace_req_start(struct pt_regs *ctx, struct request *req)
{
struct start_key key = {
.dev = ddevt(req->__RQ_DISK__),
.sector = req->__sector
};
SET_FLAGS
return __trace_req_start(key);
}
int trace_req_start_tp(struct tp_args *args)
{
struct start_key key = {
.dev = args->dev,
.sector = args->sector
};
return __trace_req_start(key);
}
// output
static int __trace_req_done(struct start_key key)
{
u64 *tsp, delta;
// fetch timestamp and calculate delta
tsp = start.lookup(&key);
if (tsp == 0) {
return 0; // missed issue
}
delta = bpf_ktime_get_ns() - *tsp;
FACTOR
// store as histogram
STORE
start.delete(&key);
return 0;
}
int trace_req_done(struct pt_regs *ctx, struct request *req)
{
struct start_key key = {
.dev = ddevt(req->__RQ_DISK__),
.sector = req->__sector
};
SET_FLAGS
return __trace_req_done(key);
}
int trace_req_done_tp(struct tp_args *args)
{
struct start_key key = {
.dev = args->dev,
.sector = args->sector
};
return __trace_req_done(key);
}
"""
# 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"
storage_str = ""
store_str = ""
if args.disks:
storage_str += "BPF_HISTOGRAM(dist, disk_key_t);"
disks_str = """
disk_key_t dkey = {};
dkey.dev = key.dev;
dkey.slot = bpf_log2l(delta);
dist.atomic_increment(dkey);
"""
store_str += disks_str
elif args.flags:
storage_str += "BPF_HISTOGRAM(dist, flag_key_t);"
store_str += """
flag_key_t fkey = {.slot = bpf_log2l(delta)};
fkey.flags = key.flags;
dist.atomic_increment(fkey);
"""
else:
storage_str += "BPF_HISTOGRAM(dist);"
store_str += "dist.atomic_increment(bpf_log2l(delta));"
if args.disk is not None:
disk_path = os.path.join('/dev', args.disk)
if not os.path.exists(disk_path):
print("no such disk '%s'" % args.disk)
exit(1)
stat_info = os.stat(disk_path)
dev = os.major(stat_info.st_rdev) << 20 | os.minor(stat_info.st_rdev)
disk_filter_str = """
if(key.dev != %s) {
return 0;
}
""" % (dev)
bpf_text = bpf_text.replace('DISK_FILTER', disk_filter_str)
else:
bpf_text = bpf_text.replace('DISK_FILTER', '')
if args.extension:
storage_str += "BPF_ARRAY(extension, ext_val_t, 1);"
store_str += """
u32 index = 0;
ext_val_t *ext_val = extension.lookup(&index);
if (ext_val) {
lock_xadd(&ext_val->total, delta);
lock_xadd(&ext_val->count, 1);
}
"""
bpf_text = bpf_text.replace("STORAGE", storage_str)
bpf_text = bpf_text.replace("STORE", store_str)
if BPF.kernel_struct_has_field(b'request', b'rq_disk') == 1:
bpf_text = bpf_text.replace('__RQ_DISK__', 'rq_disk')
else:
bpf_text = bpf_text.replace('__RQ_DISK__', 'q->disk')
if args.flags:
bpf_text = bpf_text.replace('CMD_FLAGS', 'u64 flags;')
bpf_text = bpf_text.replace('SET_FLAGS', 'key.flags = req->cmd_flags;')
else:
bpf_text = bpf_text.replace('CMD_FLAGS', '')
bpf_text = bpf_text.replace('SET_FLAGS', '')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# load BPF program
b = BPF(text=bpf_text)
if args.queued:
if BPF.get_kprobe_functions(b'__blk_account_io_start'):
b.attach_kprobe(event="__blk_account_io_start", fn_name="trace_req_start")
elif BPF.get_kprobe_functions(b'blk_account_io_start'):
b.attach_kprobe(event="blk_account_io_start", fn_name="trace_req_start")
else:
if args.flags:
# Some flags are accessible in the rwbs field (RAHEAD, SYNC and META)
# but other aren't. Disable the -F option for tracepoint for now.
print("ERROR: blk_account_io_start probe not available. Can't use -F.")
exit()
b.attach_tracepoint(tp="block:block_io_start", fn_name="trace_req_start_tp")
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")
if BPF.get_kprobe_functions(b'__blk_account_io_done'):
b.attach_kprobe(event="__blk_account_io_done", fn_name="trace_req_done")
elif BPF.get_kprobe_functions(b'blk_account_io_done'):
b.attach_kprobe(event="blk_account_io_done", fn_name="trace_req_done")
else:
if args.flags:
print("ERROR: blk_account_io_done probe not available. Can't use -F.")
exit()
b.attach_tracepoint(tp="block:block_io_done", fn_name="trace_req_done_tp")
if not args.json:
print("Tracing block device I/O... Hit Ctrl-C to end.")
# cache disk major,minor -> diskname
diskstats = "/proc/diskstats"
disklookup = {}
with open(diskstats) as stats:
for line in stats:
a = line.split()
disklookup[a[0] + "," + a[1]] = a[2]
def disk_print(d):
major = d >> 20
minor = d & ((1 << 20) - 1)
disk = str(major) + "," + str(minor)
if disk in disklookup:
diskname = disklookup[disk]
else:
diskname = "?"
return diskname
# 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")
if args.extension:
extension = b.get_table("extension")
while (1):
try:
sleep(int(args.interval))
except KeyboardInterrupt:
exiting = 1
print()
if args.json:
if args.timestamp:
print("%-8s\n" % strftime("%H:%M:%S"), end="")
if args.flags:
dist.print_json_hist(label, "flags", flags_print)
else:
dist.print_json_hist(label, "disk", disk_print)
else:
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", disk_print)
if args.extension:
total = extension[0].total
count = extension[0].count
if count > 0:
print("\navg = %ld %s, total: %ld %s, count: %ld\n" %
(total / count, label, total, label, count))
extension.clear()
dist.clear()
countdown -= 1
if exiting or countdown == 0:
exit()
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