[tools] Specify affinity and raise priority when benchmarking

tools/run_perf.py

Index: tools/run_perf.py
diff --git a/tools/run_perf.py b/tools/run_perf.py
index db4245f499fc07c3a32f435a78ec08d5f06f58a3..f2c881e7e463eb733d6d919f00263b3f76aa4938 100755
--- a/tools/run_perf.py
+++ b/tools/run_perf.py
@@ -612,6 +612,19 @@ class Platform(object):
 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
@@ -627,10 +640,11 @@ class DesktopPlatform(Platform):
     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"
@@ -822,6 +836,14 @@ def Main(args):
                     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)