perf: allow profiling of more than one run

perf: allow profiling of more than one run

By default, we still profile the first run only. However profiling more run help
to understand side effect from one run to the other. So we add an option to be
able to do so.

--- a/contrib/perf.py	Sun Apr 14 02:36:55 2024 +0200
+++ b/contrib/perf.py	Sun Apr 14 02:38:41 2024 +0200
@@ -20,7 +20,10 @@
 
 ``profile-benchmark``
   Enable profiling for the benchmarked section.
-  (The first iteration is benchmarked)
+  (by default, the first iteration is benchmarked)
+
+``profiled-runs``
+  list of iteration to profile (starting from 0)
 
 ``run-limits``
   Control the number of runs each benchmark will perform. The option value
@@ -318,6 +321,11 @@
     )
     configitem(
         b'perf',
+        b'profiled-runs',
+        default=mercurial.configitems.dynamicdefault,
+    )
+    configitem(
+        b'perf',
         b'run-limits',
         default=mercurial.configitems.dynamicdefault,
         experimental=True,
@@ -354,7 +362,7 @@
     )
     configitem(
         b'perf',
-        b'profile-benchmark',
+        b'profiled-runs',
         default=mercurial.configitems.dynamicdefault,
     )
     configitem(
@@ -491,9 +499,12 @@
         limits = DEFAULTLIMITS
 
     profiler = None
+    profiled_runs = set()
     if profiling is not None:
         if ui.configbool(b"perf", b"profile-benchmark", False):
-            profiler = profiling.profile(ui)
+            profiler = lambda: profiling.profile(ui)
+            for run in ui.configlist(b"perf", b"profiled-runs", [0]):
+                profiled_runs.add(int(run))
 
     prerun = getint(ui, b"perf", b"pre-run", 0)
     t = functools.partial(
@@ -503,6 +514,7 @@
         limits=limits,
         prerun=prerun,
         profiler=profiler,
+        profiled_runs=profiled_runs,
     )
     return t, fm
 
@@ -547,13 +559,14 @@
     limits=DEFAULTLIMITS,
     prerun=0,
     profiler=None,
+    profiled_runs=(0,),
 ):
     gc.collect()
     results = []
     begin = util.timer()
     count = 0
     if profiler is None:
-        profiler = NOOPCTX
+        profiler = lambda: NOOPCTX
     for i in range(prerun):
         if setup is not None:
             setup()
@@ -561,13 +574,16 @@
             func()
     keepgoing = True
     while keepgoing:
+        if count in profiled_runs:
+            prof = profiler()
+        else:
+            prof = NOOPCTX
         if setup is not None:
             setup()
         with context():
-            with profiler:
+            with prof:
                 with timeone() as item:
                     r = func()
-        profiler = NOOPCTX
         count += 1
         results.append(item[0])
         cstop = util.timer()

--- a/tests/test-contrib-perf.t	Sun Apr 14 02:36:55 2024 +0200
+++ b/tests/test-contrib-perf.t	Sun Apr 14 02:38:41 2024 +0200
@@ -59,8 +59,11 @@
     number of run to perform before starting measurement.
   
   "profile-benchmark"
-    Enable profiling for the benchmarked section. (The first iteration is
-    benchmarked)
+    Enable profiling for the benchmarked section. (by default, the first
+    iteration is benchmarked)
+  
+  "profiled-runs"
+    list of iteration to profile (starting from 0)
   
   "run-limits"
     Control the number of runs each benchmark will perform. The option value