tools/biolatency: Add disk filter support (iovisor#4026)

Sometimes, I just want to focus on a specified disk rather than all disks or per-disk. Refer to libbpf-tools/biolatency, this patch try to add disk filter support.

man/man8/biolatency.8

@@ -2,7 +2,7 @@
 .SH NAME
 biolatency \- Summarize block device I/O latency as a histogram.
 .SH SYNOPSIS
-.B biolatency [\-h] [\-F] [\-T] [\-Q] [\-m] [\-D] [\-e] [interval [count]]
+.B biolatency [\-h] [\-F] [\-T] [\-Q] [\-m] [\-D] [\-F] [\-e] [\-j] [\-d DISK] [interval [count]]
 .SH DESCRIPTION
 biolatency traces block device I/O (disk I/O), and records the distribution
 of I/O latency (time). This is printed as a histogram either on Ctrl-C, or
@@ -42,6 +42,9 @@ Print a histogram dictionary
 \-e
 Show extension summary(total, average)
 .TP
+\-d DISK
+Trace this disk only
+.TP
 interval
 Output interval, in seconds.
 .TP
@@ -108,6 +111,6 @@ Linux
 .SH STABILITY
 Unstable - in development.
 .SH AUTHOR
-Brendan Gregg
+Brendan Gregg, Rocky Xing
 .SH SEE ALSO
 biosnoop(8)

tools/biolatency.py

@@ -4,18 +4,20 @@
 # 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] [interval] [count]
+# 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.
 
 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:
@@ -27,6 +29,7 @@
  ./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",
@@ -52,6 +55,8 @@
  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)
@@ -87,6 +92,8 @@
 // time block I/O
 int trace_req_start(struct pt_regs *ctx, struct request *req)
 {
+ DISK_FILTER
+
  u64 ts = bpf_ktime_get_ns();
  start.update(&req, &ts);
  return 0;
@@ -149,6 +156,33 @@
  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)
+ major = os.major(stat_info.st_rdev)
+ minor = os.minor(stat_info.st_rdev)
+
+ disk_field_str = ""
+ if BPF.kernel_struct_has_field(b'request', b'rq_disk') == 1:
+ disk_field_str = 'req->rq_disk'
+ else:
+ disk_field_str = 'req->q->disk'
+
+ disk_filter_str = """
+ struct gendisk *disk = %s;
+ if (!(disk->major == %d && disk->first_minor == %d)) {
+ return 0;
+ }
+ """ % (disk_field_str, major, minor)
+
+ 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);"
  bpf_text = bpf_text.replace('EXTENSION', """

tools/biolatency_example.txt

@@ -352,24 +352,25 @@ The -j with -m prints a millisecond histogram dictionary. The `value_type` key i
 USAGE message:
 
 # ./biolatency -h
-usage: biolatency.py [-h] [-T] [-Q] [-m] [-D] [-F] [-j]
-  [interval] [count]
+usage: biolatency.py [-h] [-T] [-Q] [-m] [-D] [-F] [-e] [-j] [-d DISK]
+ [interval] [count]
 
 Summarize block device I/O latency as a histogram
 
 positional arguments:
- interval output interval, in seconds
- count number of outputs
+ interval  output interval, in seconds
+ count  number of outputs
 
 optional arguments:
- -h, --help show this help message and exit
- -T, --timestamp include timestamp on output
- -Q, --queued include OS queued time in I/O time
- -m, --milliseconds millisecond histogram
- -D, --disks print a histogram per disk device
- -F, --flags print a histogram per set of I/O flags
- -e, --extension also show extension summary(total, average)
- -j, --json json output
+ -h, --help show this help message and exit
+ -T, --timestamp include timestamp on output
+ -Q, --queued include OS queued time in I/O time
+ -m, --milliseconds millisecond histogram
+ -D, --disks print a histogram per disk device
+ -F, --flags print a histogram per set of I/O flags
+ -e, --extension summarize average/total value
+ -j, --json json output
+ -d DISK, --disk DISK Trace this disk only
 
 examples:
  ./biolatency # summarize block I/O latency as a histogram
@@ -380,3 +381,4 @@ examples:
  ./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