add parsimonious sem variant

bench/emper.py

@@ -463,6 +463,9 @@ FLAVORS: Flavors = {
         'meson_options': '-Dworker_wakeup_strategy=all',
         'patches': ['fix_free_vs_delete.patch', 'wakeup-condvar.patch'],
     },
+    'parsimonious-sem': {
+        'meson_options': '-Dsleep_sem_threshold=0'
+    },
     'wakeup-futex2': {
         'meson_options': '-Dwakeup_semaphore_implementation=futex2'
     },