Allow stacks to be captured from /usr/bin/sample on macOS

Author: alblue

stackcollapse-sample.awk

@@ -0,0 +1,231 @@
+#!/usr/bin/awk -f
+#
+# Uses MacOS' /usr/bin/sample to generate a flamegraph of a process
+#
+# Usage:
+#
+# sudo sample [pid] -file /dev/stdout | stackcollapse-sample.awk | flamegraph.pl
+#
+# Options:
+#
+# The output will show the name of the library/framework at the call-site
+# with the form AppKit`NSApplication or libsystem`start_wqthread.
+#
+# If showing the framework or library name is not required, pass
+# MODULES=0 as an argument of the sample program.
+#
+# The generated SVG will be written to the output stream, and can be piped
+# into flamegraph.pl directly, or written to a file for conversion later.
+#
+# ---
+#
+# Copyright (c) 2017, Apple Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# 1. Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+#
+# 2. Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+BEGIN {
+
+  # Command line options
+  MODULES = 1       # Allows the user to enable/disable printing of modules.
+
+  # Internal variables
+  _FOUND_STACK = 0  # Found the stack traces in the output.
+  _LEVEL = -1       # The current level of indentation we are running.
+
+  # The set of symbols to ignore for 'waiting' threads, for ease of use.
+  # This will hide waiting threads from the view, making it easier to
+  # see what is actually running in the sample. These may be adjusted
+  # as necessary or appended to if other symbols need to be filtered out.
+
+  _IGNORE["libsystem_kernel`__psynch_cvwait"] = 1
+  _IGNORE["libsystem_kernel`__select"] = 1
+  _IGNORE["libsystem_kernel`__semwait_signal"] = 1
+  _IGNORE["libsystem_kernel`__ulock_wait"] = 1
+  _IGNORE["libsystem_kernel`__wait4"] = 1
+  _IGNORE["libsystem_kernel`__workq_kernreturn"] = 1
+  _IGNORE["libsystem_kernel`kevent"] = 1
+  _IGNORE["libsystem_kernel`mach_msg_trap"] = 1
+  _IGNORE["libsystem_kernel`read"] = 1
+  _IGNORE["libsystem_kernel`semaphore_wait_trap"] = 1
+
+  # The same set of symbols as above, without the module name.
+  _IGNORE["__psynch_cvwait"] = 1
+  _IGNORE["__select"] = 1
+  _IGNORE["__semwait_signal"] = 1
+  _IGNORE["__ulock_wait"] = 1
+  _IGNORE["__wait4"] = 1
+  _IGNORE["__workq_kernreturn"] = 1
+  _IGNORE["kevent"] = 1
+  _IGNORE["mach_msg_trap"] = 1
+  _IGNORE["read"] = 1
+  _IGNORE["semaphore_wait_trap"] = 1
+
+}
+
+# This is the first line in the /usr/bin/sample output that indicates the
+# samples follow subsequently. Until we see this line, the rest is ignored.
+
+/^Call graph/ {
+  _FOUND_STACK = 1
+}
+
+# This is found when we have reached the end of the stack output.
+# Identified by the string "Total number in stack (...)".
+
+/^Total number/ {
+  _FOUND_STACK = 0
+  printStack(_NEST,0)
+}
+
+# Prints the stack from FROM to TO (where FROM > TO)
+# Called when indenting back from a previous level, or at the end
+# of processing to flush the last recorded sample
+
+function printStack(FROM,TO) {
+
+  # We ignore certain blocking wait states, in the absence of being
+  # able to filter these threads from collection, otherwise
+  # we'll end up with many threads of equal length that represent
+  # the total time the sample was collected.
+  #
+  # Note that we need to collect the information to ensure that the
+  # timekeeping for the parental functions is appropriately adjusted
+  # so we just avoid printing it out when that occurs.
+  _PRINT_IT = !_IGNORE[_NAMES[FROM]]
+
+  # We run through all the names, from the root to the leaf, so that
+  # we generate a line that flamegraph.pl will like, of the form:
+  # Thread1234;example`main;example`otherFn 1234
+
+  for(l = FROM; l>=TO; l--) {
+    if (_PRINT_IT) {
+      printf("%s", _NAMES[0])
+      for(i=1; i<=l; i++) {
+        printf(";%s", _NAMES[i])
+      }
+      print " " _TIMES[l]
+    }
+
+    # We clean up our current state to avoid bugs.
+    delete _NAMES[l]
+    delete _TIMES[l]
+  }
+}
+
+# This is where we process each line, of the form:
+#  5130 Thread_8749954
+#    + 5130 start_wqthread  (in libsystem_pthread.dylib) ...
+#    +   4282 _pthread_wqthread  (in libsystem_pthread.dylib) ...
+#    +   ! 4282 __doworkq_kernreturn  (in libsystem_kernel.dylib) ...
+#    +   848 _pthread_wqthread  (in libsystem_pthread.dylib) ...
+#    +     848 __doworkq_kernreturn  (in libsystem_kernel.dylib) ...
+
+_FOUND_STACK && match($0,/^    [^0-9]*[0-9]/) {
+
+  # We maintain two counters:
+  #   _LEVEL: the high water mark of the indentation level we have seen.
+  #   _NEST:  the current indentation level.
+  #
+  # We keep track of these two levels such that when the nesting level
+  # decreases, we print out the current state of where we are.
+
+  _NEST=(RLENGTH-5)/2
+  sub(/^[^0-9]*/,"") # Normalise the leading content so we start with time.
+  _TIME=$1           # The time recorded by 'sample', first integer value.
+
+  # The function name is in one or two parts, depending on what kind of
+  # function it is.
+  #
+  # If it is a standard C or C++ function, it will be of the form:
+  #  exampleFunction
+  #  Example::Function
+  #
+  # If it is an Objective-C funtion, it will be of the form:
+  #  -[NSExample function]
+  #  +[NSExample staticFunction]
+  #  -[NSExample function:withParameter]
+  #  +[NSExample staticFunction:withParameter:andAnother]
+
+  _FN1 = $2
+  _FN2 = $3
+
+  # If it is a standard C or C++ function then the following word will
+  # either be blank, or the text '(in', so we jut use the first one:
+
+  if (_FN2 == "(in" || _FN2 == "") {
+    _FN =_FN1
+  } else {
+    # Otherwise we concatenate the first two parts with .
+    _FN = _FN1 "." _FN2
+  }
+
+  # Modules are shown with '(in libfoo.dylib)' or '(in AppKit)'
+
+  _MODULE = ""
+  match($0, /\(in [^)]*\)/)
+
+  if (RSTART > 0 && MODULES) {
+
+    # Strip off the '(in ' (4 chars) and the final ')' char (1 char)
+    _MODULE = substr($0, RSTART+4, RLENGTH-5)
+
+    # Remove the .dylib function, since it adds no value.
+    gsub(/\.dylib/, "", _MODULE)
+
+    # The function name is 'module`functionName'
+    _FN = _MODULE "`" _FN
+  }
+
+  # Now we have set up the variables, we can decide how to apply it
+  # If we are descending in the nesting, we don't print anything out:
+  # a
+  # ab
+  # abc
+  #
+  # We only print out something when we go back a level, or hit the end:
+  # abcd
+  # abe < prints out the stack up until this point, i.e. abcd
+
+  # We store a pair of arrays, indexed by the nesting level:
+  #
+  #  _TIMES - a list of the time reported to that function
+  #  _NAMES - a list of the function names for each current stack trace
+
+  # If we are backtracking, we need to flush the current output.
+  if (_NEST <= _LEVEL) {
+    printStack(_LEVEL,_NEST)
+  }
+
+  # Record the name and time of the function where we are.
+  _NAMES[_NEST] = _FN
+  _TIMES[_NEST] = _TIME
+
+  # We subtract the time we took from our parent so we don't double count.
+  if (_NEST > 0) {
+    _TIMES[_NEST-1] -= _TIME
+  }
+
+  # Raise the high water mark of the level we have reached.
+  _LEVEL = _NEST
+}