[Git][ghc/ghc][master] Profiling: Adds an option to not start time profiling at startup

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
5077416e by Javier Sagredo at 2024-01-16T15:40:06-05:00
Profiling: Adds an option to not start time profiling at startup

Using the functionality provided by
d89deeba47ce04a5198a71fa4cbc203fe2c90794, this patch creates a new rts
flag `--no-automatic-time-samples` which disables the time profiling
when starting a program. It is then expected that the user starts it
whenever it is needed.

Fixes #24337

- - - - -


6 changed files:

- docs/users_guide/9.10.1-notes.rst
- docs/users_guide/profiling.rst
- libraries/base/src/GHC/Profiling.hs
- rts/Profiling.c
- rts/RtsFlags.c
- rts/include/rts/Flags.h


Changes:

=====================================
docs/users_guide/9.10.1-notes.rst
=====================================
@@ -140,6 +140,9 @@ Runtime system
   See :ghc-ticket:`23340`.
   :rts-flag:`--nonmoving-dense-allocator-count=⟨count⟩` has been added to fine-tune this behaviour.
 
+- Add a :rts-flag:`--no-automatic-time-samples` flag which stops time profiling samples being automatically started on
+  startup. Time profiling can be controlled manually using functions in ``GHC.Profiling``.
+
 ``base`` library
 ~~~~~~~~~~~~~~~~
 


=====================================
docs/users_guide/profiling.rst
=====================================
@@ -1009,6 +1009,13 @@ There are three more options which relate to heap profiling:
     option is enabled, it's expected that the user will manually start heap
     profiling or request specific samples using functions from ``GHC.Profiling``.
 
+.. rts-flag:: --no-automatic-time-samples
+
+    :since: 9.10.1
+
+    Don't start time profiling from the start of program execution. If this
+    option is enabled, it's expected that the user will manually start time
+    profiling or request specific samples using functions from ``GHC.Profiling``.
 
 .. rts-flag:: --null-eventlog-writer
 


=====================================
libraries/base/src/GHC/Profiling.hs
=====================================
@@ -20,7 +20,7 @@ import GHC.Base
 foreign import ccall stopProfTimer :: IO ()
 
 -- | Start attributing ticks to cost centres. This is called by the RTS on
--- startup.
+-- startup but can be disabled using the rts flag @--no-automatic-time-samples at .
 --
 -- @since 4.7.0.0
 foreign import ccall startProfTimer :: IO ()


=====================================
rts/Profiling.c
=====================================
@@ -296,8 +296,10 @@ void
 initTimeProfiling(void)
 {
     traceProfBegin();
-    /* Start ticking */
-    startProfTimer();
+    if (RtsFlags.ProfFlags.startTimeProfileAtStartup) {
+        /* Start ticking */
+        startProfTimer();
+    }
 };
 
 void


=====================================
rts/RtsFlags.c
=====================================
@@ -216,6 +216,7 @@ void initRtsFlagsDefaults(void)
     RtsFlags.ProfFlags.doHeapProfile      = false;
     RtsFlags.ProfFlags.heapProfileInterval = USToTime(100000); // 100ms
     RtsFlags.ProfFlags.startHeapProfileAtStartup = true;
+    RtsFlags.ProfFlags.startTimeProfileAtStartup = true;
 
 #if defined(PROFILING)
     RtsFlags.ProfFlags.showCCSOnException = false;
@@ -1154,6 +1155,12 @@ error = true;
                       RtsFlags.ProfFlags.startHeapProfileAtStartup = false;
                       break;
                   }
+                  else if (strequal("no-automatic-time-samples",
+                               &rts_argv[arg][2])) {
+                      OPTION_SAFE;
+                      RtsFlags.ProfFlags.startTimeProfileAtStartup = false;
+                      break;
+                  }
                   else {
                       OPTION_SAFE;
                       errorBelch("unknown RTS option: %s",rts_argv[arg]);


=====================================
rts/include/rts/Flags.h
=====================================
@@ -148,6 +148,7 @@ typedef struct _PROFILING_FLAGS {
     Time        heapProfileInterval; /* time between samples */
     uint32_t    heapProfileIntervalTicks; /* ticks between samples (derived) */
     bool        startHeapProfileAtStartup; /* true if we start profiling from program startup */
+    bool        startTimeProfileAtStartup; /* true if we start profiling from program startup */
 
 
     bool        showCCSOnException;



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5077416e12cf480fb2048928aa51fa4c8fc22cf1

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5077416e12cf480fb2048928aa51fa4c8fc22cf1
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