Communicate the used core spec to executed program

This septs a REBENCH_DENOISE_CORE_SET environment variable for the command executed by denoise.

It can be used, for instance to ensure that pinning selects cores that are part of the spec.

The test mode checks whether the core spec is consistent.

Signed-off-by: Stefan Marr <git@stefan-marr.de>

rebench/denoise.py

@@ -270,7 +270,7 @@ def _restore_standard_settings(num_cores, use_shielding):
             "shielding": shielding}
 
 
-def _exec(use_nice, use_shielding, args):
+def _exec(num_cores, use_nice, use_shielding, args):
     cmdline = []
     if use_shielding:
         cmdline += ["cset", "shield", "--exec", "--"]
@@ -280,7 +280,15 @@ def _exec(use_nice, use_shielding, args):
 
     # the first element of cmdline is ignored as argument, since it's the file argument, too
     cmd = cmdline[0]
-    os.execvp(cmd, cmdline)
+
+    # communicate the used core spec to executed command as part of its environment
+    env = os.environ.copy()
+    min_cores = _shield_lower_bound(num_cores)
+    max_cores = _shield_upper_bound(num_cores)
+    core_spec = "%d-%d" % (min_cores, max_cores)
+    env['REBENCH_DENOISE_CORE_SET'] = core_spec
+
+    os.execvpe(cmd, cmdline, env)
 
 
 def _calculate(core_id):
@@ -302,6 +310,14 @@ def _test(num_cores):
     pool = Pool(core_cnt)
 
     print("Test on %d cores" % core_cnt)
+
+    core_spec = "%d-%d" % (lower, upper)
+    env_spec = os.environ.get('REBENCH_DENOISE_CORE_SET', None)
+    if core_spec != env_spec:
+        print("Core Spec set by denoise was: ", env_spec)
+        print("Locally determined one was: ", core_spec)
+        print("The specs did not match!")
+
     try:
         pool.map(_calculate, range(0, core_cnt))
     except KeyboardInterrupt:
@@ -346,7 +362,7 @@ def main_func():
     elif args.command == 'restore':
         result = _restore_standard_settings(num_cores, args.use_shielding)
     elif args.command == 'exec':
-        _exec(args.use_nice, args.use_shielding, remaining_args)
+        _exec(num_cores, args.use_nice, args.use_shielding, remaining_args)
     elif args.command == 'test':
         _test(num_cores)
     else: