tools/biosnoop: Add disk filter support

Limnotation · Jul 3, 2022 · f1b769b · f1b769b
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diff --git a/man/man8/biosnoop.8 b/man/man8/biosnoop.8
@@ -2,7 +2,7 @@
 .SH NAME
 biosnoop \- Trace block device I/O and print details incl. issuing PID.
 .SH SYNOPSIS
-.B biosnoop [\-hQ]
+.B biosnoop [\-h] [\-Q] [\-d DISK]
 .SH DESCRIPTION
 This tools traces block device I/O (disk I/O), and prints a one-line summary
 for each I/O showing various details. These include the latency from the time of
@@ -29,6 +29,9 @@ Print usage message.
 .TP
 \-Q
 Include a column showing the time spent queued in the OS.
+.TP
+\-d DISK
+Trace this disk only.
 .SH EXAMPLES
 .TP
 Trace all block device I/O and print a summary line per I/O:
@@ -82,6 +85,6 @@ Linux
 .SH STABILITY
 Unstable - in development.
 .SH AUTHOR
-Brendan Gregg
+Brendan Gregg, Rocky Xing
 .SH SEE ALSO
 disksnoop(8), iostat(1)
diff --git a/tools/biosnoop.py b/tools/biosnoop.py
@@ -12,23 +12,28 @@
 #
 # 16-Sep-2015 Brendan Gregg Created this.
 # 11-Feb-2016 Allan McAleavy updated for BPF_PERF_OUTPUT
+# 21-Jun-2022 Rocky Xing Added disk filter support.
 
 from __future__ import print_function
 from bcc import BPF
 import re
 import argparse
+import os
 
 # arguments
 examples = """examples:
  ./biosnoop # trace all block I/O
  ./biosnoop -Q # include OS queued time
+ ./biolatency -d sdc # trace sdc only
 """
 parser = argparse.ArgumentParser(
  description="Trace block I/O",
  formatter_class=argparse.RawDescriptionHelpFormatter,
  epilog=examples)
 parser.add_argument("-Q", "--queue", action="store_true",
  help="include OS queued time")
+parser.add_argument("-d", "--disk", type=str,
+ help="Trace this disk only")
 parser.add_argument("--ebpf", action="store_true",
  help=argparse.SUPPRESS)
 args = parser.parse_args()
@@ -70,6 +75,8 @@
 // cache PID and comm by-req
 int trace_pid_start(struct pt_regs *ctx, struct request *req)
 {
+ DISK_FILTER
+
  struct val_t val = {};
  u64 ts;
 
@@ -86,6 +93,8 @@
 // time block I/O
 int trace_req_start(struct pt_regs *ctx, struct request *req)
 {
+ DISK_FILTER
+
  struct start_req_t start_req = {
  .ts = bpf_ktime_get_ns(),
  .data_len = req->__data_len
@@ -160,6 +169,34 @@
  bpf_text = bpf_text.replace('__RQ_DISK__', 'rq_disk')
 else:
  bpf_text = bpf_text.replace('__RQ_DISK__', 'q->disk')
+
+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 debug or args.ebpf:
  print(bpf_text)
  if args.ebpf:

diff --git a/tools/biosnoop_example.txt b/tools/biosnoop_example.txt
@@ -64,14 +64,16 @@ TIME(s) COMM PID DISK T SECTOR BYTES QUE(ms) LAT(ms)
 
 USAGE message:
 
-usage: biosnoop.py [-h] [-Q]
+usage: biosnoop.py [-h] [-Q] [-d DISK]
 
 Trace block I/O
 
 optional arguments:
- -h, --help show this help message and exit
- -Q, --queue include OS queued time
+ -h, --help show this help message and exit
+ -Q, --queue include OS queued time
+ -d DISK, --disk DISK Trace this disk only
 
 examples:
  ./biosnoop # trace all block I/O
  ./biosnoop -Q # include OS queued time
+ ./biolatency -d sdc # trace sdc only