[tools] Specify affinity and raise priority when benchmarking

tools/run_perf.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Performance runner for d8.
 
 Call e.g. with tools/run-perf.py --arch ia32 some_suite.json
 
@@ skipping 594 matching lines @@
     stdout = self._Run(runnable, count, no_patch=False)
     if self.shell_dir_no_patch:
       return stdout, self._Run(runnable, count, no_patch=True)
     else:
       return stdout, None
 
 
 class DesktopPlatform(Platform):
   def __init__(self, options):
     super(DesktopPlatform, self).__init__(options)
+    self.command_prefix = []
+    if options.prioritize or options.affinitize != None:
+      self.command_prefix = ["sudo", "schedtool"]
+      if options.prioritize:
+        self.command_prefix += ["-p", "-20"]

[Michael Achenbach, 2016/04/27 14:55:00]

My documentation says:
    -p STATIC_PRIORITY    usually 1-99; only for FIFO or RR
                          higher numbers means higher priority

[Mircea Trofin, 2016/04/27 15:56:35]

Ugh. should be -n, not -p. Thanks.

+      if options.affinitize != None:
+      # schedtool expects a bit pattern when setting affinity, where each
+      # bit set to '1' corresponds to a core where the process may run on.
+      # 0 corresponds to CPU 0. Since the 'affinitize' parameter is a core number, we need
+      # to map to said bit pattern.
+        core = (1 << int(options.affinitize)) - 1
+        self.command_prefix += ["-a", str(core)]

[Michael Achenbach, 2016/04/27 14:55:00]

So if options.affinitize == 2, this is set to "-a 3". Is that what the tool
wants or a binary bit pattern like 011?

I also wonder, setting several bits means several cores right? The description
below says "_the_ specified core" or did I get something wrong?

Which one is core 0 exactly?
011
  ^
or
011
^

According to the CL description, core 0 should be avoided. Is it?

[Mircea Trofin, 2016/04/27 15:56:35]

Oh, that's a bug, indeed. It should be  core = if options.affinitize == 0: 0
else (1 << (options.affinitize - 1) )

I'd still let developers specify core 0 if they so wish. I'll make the commit
comment more clear that way.

[Michael Achenbach, 2016/04/27 17:23:29]

Could you add in a comment an example of how this exactly looks like? E.g. for
core number 3 and for 0 and what is expected to be passed to schedtool.

[Mircea Trofin, 2016/04/28 02:07:24]

Done.

+      self.command_prefix += ["-e"]
 
   def PreExecution(self):
     pass
 
   def PostExecution(self):
     pass
 
   def PreTests(self, node, path):
     if isinstance(node, RunnableConfig):
       node.ChangeCWD(path)
 
   def _Run(self, runnable, count, no_patch=False):
     suffix = ' - without patch' if no_patch else ''
     shell_dir = self.shell_dir_no_patch if no_patch else self.shell_dir
     title = ">>> %%s (#%d)%s:" % ((count + 1), suffix)
+    command = self.command_prefix + runnable.GetCommand(shell_dir, self.extra_flags)
     try:
       output = commands.Execute(
-          runnable.GetCommand(shell_dir, self.extra_flags),
-          timeout=runnable.timeout,
+        command,
+        timeout=runnable.timeout,
       )
     except OSError as e:  # pragma: no cover
       print title % "OSError"
       print e
       return ""
     print title % "Stdout"
     print output.stdout
     if output.stderr:  # pragma: no cover
       # Print stderr for debugging.
       print title % "Stderr"
@@ skipping 171 matching lines @@
                     help="Path to a file for storing json results from run "
                          "without patch.")
   parser.add_option("--outdir", help="Base directory with compile output",
                     default="out")
   parser.add_option("--outdir-no-patch",
                     help="Base directory with compile output without patch")
   parser.add_option("--binary-override-path",
                     help="JavaScript engine binary. By default, d8 under "
                     "architecture-specific build dir. "
                     "Not supported in conjunction with outdir-no-patch.")
+  parser.add_option("--prioritize",
+                    help="Raise the priority to nice -20 for the benchmarking process."
+                    "Requires Linux, schedtool, and sudo privileges.",
+                    default=False, action="store_true")
+  parser.add_option("--affinitize",
+                    help="Run benchmarking process on the specified core."
+                    "Requires Linux, schedtool, and sudo privileges.",
+                    default=None)
 
   (options, args) = parser.parse_args(args)
 
   if len(args) == 0:  # pragma: no cover
     parser.print_help()
     return 1
 
   if options.arch in ["auto", "native"]:  # pragma: no cover
     options.arch = ARCH_GUESS
 
@@ skipping 90 matching lines @@
 
   if options.json_test_results_no_patch:
     results_no_patch.WriteToFile(options.json_test_results_no_patch)
   else:  # pragma: no cover
     print results_no_patch
 
   return min(1, len(results.errors))
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(Main(sys.argv[1:]))