#!/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 #include 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()