tools/profile: add -L option to support filtering on TID (iovisor#2315)

tools/profile already supports "-p PID" to filter on PID (tgid in kernel).
Now add "-L TID" to profile thread with this TID only (pid in kernel).

man/man8/profile.8

@@ -2,7 +2,7 @@
 .SH NAME
 profile \- Profile CPU usage by sampling stack traces. Uses Linux eBPF/bcc.
 .SH SYNOPSIS
-.B profile [\-adfh] [\-p PID] [\-U | \-K] [\-F FREQUENCY | \-c COUNT]
+.B profile [\-adfh] [\-p PID | \-L TID] [\-U | \-K] [\-F FREQUENCY | \-c COUNT]
 .B [\-\-stack\-storage\-size COUNT] [duration]
 .SH DESCRIPTION
 This is a CPU profiler. It works by taking samples of stack traces at timed
@@ -28,8 +28,10 @@ for an older version that may work on Linux 4.6 - 4.8.
 Print usage message.
 .TP
 \-p PID
-Trace this process ID only (filtered in-kernel). Without this, all CPUs are
-profiled.
+Trace this process ID only (filtered in-kernel).
+.TP
+\-L TID
+Trace this thread ID only (filtered in-kernel).
 .TP
 \-F frequency
 Frequency to sample stacks.
@@ -80,10 +82,14 @@ Profile 1 in a million events for 5 seconds only:
 #
 .B profile -c 1000000 5
 .TP
-Profile PID 181 only:
+Profile process with PID 181 only:
 #
 .B profile -p 181
 .TP
+Profile thread with TID 181 only:
+#
+.B profile -L 181
+.TP
 Profile for 5 seconds and output in folded stack format (suitable as input for flame graphs), including a delimiter between kernel and user stacks:
 #
 .B profile -df 5

tools/profile.py

@@ -34,7 +34,6 @@
 import signal
 import os
 import errno
-import multiprocessing
 
 #
 # Process Arguments
@@ -69,7 +68,8 @@ def stack_id_err(stack_id):
  ./profile -c 1000000 # profile stack traces every 1 in a million events
  ./profile 5 # profile at 49 Hertz for 5 seconds only
  ./profile -f 5 # output in folded format for flame graphs
- ./profile -p 185 # only profile threads for PID 185
+ ./profile -p 185 # only profile process with PID 185
+ ./profile -L 185 # only profile thread with TID 185
  ./profile -U # only show user space stacks (no kernel)
  ./profile -K # only show kernel space stacks (no user)
 """
@@ -79,7 +79,9 @@ def stack_id_err(stack_id):
  epilog=examples)
 thread_group = parser.add_mutually_exclusive_group()
 thread_group.add_argument("-p", "--pid", type=positive_int,
- help="profile this PID only")
+ help="profile process with this PID only")
+thread_group.add_argument("-L", "--tid", type=positive_int,
+ help="profile thread with this TID only")
 # TODO: add options for user/kernel threads only
 stack_group = parser.add_mutually_exclusive_group()
 stack_group.add_argument("-U", "--user-stacks-only", action="store_true",
@@ -144,15 +146,18 @@ def stack_id_err(stack_id):
 // This code gets a bit complex. Probably not suitable for casual hacking.
 
 int do_perf_event(struct bpf_perf_event_data *ctx) {
- u32 pid = bpf_get_current_pid_tgid() >> 32;
+ u64 id = bpf_get_current_pid_tgid();
+ u32 tgid = id >> 32;
+ u32 pid = id;
+
  if (IDLE_FILTER)
  return 0;
 
  if (!(THREAD_FILTER))
  return 0;
 
  // create map key
- struct key_t key = {.pid = pid};
+ struct key_t key = {.pid = tgid};
  bpf_get_current_comm(&key.name, sizeof(key.name));
 
  // get stacks
@@ -197,13 +202,14 @@ def stack_id_err(stack_id):
  idle_filter = "0"
 bpf_text = bpf_text.replace('IDLE_FILTER', idle_filter)
 
-# set thread filter
+# set process/thread filter
 thread_context = ""
-perf_filter = "-a"
 if args.pid is not None:
  thread_context = "PID %s" % args.pid
- thread_filter = 'pid == %s' % args.pid
- perf_filter = '-p %s' % args.pid
+ thread_filter = 'tgid == %s' % args.pid
+elif args.tid is not None:
+ thread_context = "TID %s" % args.tid
+ thread_filter = 'pid == %s' % args.tid
 else:
  thread_context = "all threads"
  thread_filter = '1'

tools/profile_example.txt

@@ -707,7 +707,7 @@ Run ./profile -h to see the default.
 USAGE message:
 
 # ./profile -h
-usage: profile.py [-h] [-p PID] [-U | -K] [-F FREQUENCY | -c COUNT] [-d] [-a]
+usage: profile.py [-h] [-p PID | -L TID] [-U | -K] [-F FREQUENCY | -c COUNT] [-d] [-a]
  [-I] [-f] [--stack-storage-size STACK_STORAGE_SIZE] [-C CPU]
  [duration]
 
@@ -718,7 +718,8 @@ positional arguments:
 
 optional arguments:
  -h, --help show this help message and exit
- -p PID, --pid PID profile this PID only
+ -p PID, --pid PID profile process with this PID only
+ -L TID, --tid TID profile thread with this TID only
  -U, --user-stacks-only
  show stacks from user space only (no kernel space
  stacks)
@@ -745,6 +746,7 @@ examples:
  ./profile -c 1000000 # profile stack traces every 1 in a million events
  ./profile 5 # profile at 49 Hertz for 5 seconds only
  ./profile -f 5 # output in folded format for flame graphs
- ./profile -p 185 # only profile threads for PID 185
+ ./profile -p 185 # only profile process with PID 185
+ ./profile -L 185 # only profile thread with TID 185
  ./profile -U # only show user space stacks (no kernel)
  ./profile -K # only show kernel space stacks (no user)