[Git][ghc/ghc][wip/T22264] 6 commits: nonmoving: Add missing no-op in busy-wait loop

[Ben Gamari (@bgamari)]

Ben Gamari pushed to branch wip/T22264 at Glasgow Haskell Compiler / GHC


Commits:
ae95ecac by Ben Gamari at 2022-12-04T16:18:47-05:00
nonmoving: Add missing no-op in busy-wait loop

- - - - -
4bb3c523 by Ben Gamari at 2022-12-04T16:19:25-05:00
nonmoving: Clarify comment

- - - - -
f885b896 by Ben Gamari at 2022-12-04T16:41:15-05:00
nonmoving: Don't push if nonmoving collector isn't enabled

- - - - -
d2b42867 by Ben Gamari at 2022-12-04T19:54:23-05:00
setNumCapabilities

- - - - -
ba130fcd by Ben Gamari at 2022-12-04T19:54:34-05:00
nonmovingMark: noop

- - - - -
8ce0eb1f by Ben Gamari at 2022-12-04T19:54:44-05:00
nonmoving: Disable shortcutting

- - - - -


6 changed files:

- libraries/base/GHC/Conc/Sync.hs
- rts/Schedule.c
- rts/include/rts/Threads.h
- rts/sm/NonMoving.h
- rts/sm/NonMovingMark.c
- rts/sm/NonMovingShortcut.c


Changes:

=====================================
libraries/base/GHC/Conc/Sync.hs
=====================================
@@ -380,10 +380,15 @@ to avoid contention with other processes in the machine.
 setNumCapabilities :: Int -> IO ()
 setNumCapabilities i
   | i <= 0    = failIO $ "setNumCapabilities: Capability count ("++show i++") must be positive"
-  | otherwise = c_setNumCapabilities (fromIntegral i)
+  | otherwise = do
+      ret <- c_setNumCapabilities (fromIntegral i)
+      case ret of
+        0 -> return ()
+        1 -> yield >> setNumCapabilities i
+        _ -> failIO $ "setNumCapabilities: Unknown result"
 
 foreign import ccall safe "setNumCapabilities"
-  c_setNumCapabilities :: CUInt -> IO ()
+  c_setNumCapabilities :: CUInt -> IO CInt
 
 -- | Returns the number of CPUs that the machine has
 --


=====================================
rts/Schedule.c
=====================================
@@ -2212,9 +2212,12 @@ forkProcess(HsStablePtr *entry
  * Finally we release the Capabilities we are holding, and start
  * worker Tasks on the new Capabilities we created.
  *
+ * One wrinkle here is that we must also ensure that we don't change the
+ * capability count while the nonmoving mark thread is active.
+ *
  * ------------------------------------------------------------------------- */
 
-void
+int
 setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS)
 {
 #if !defined(THREADED_RTS)
@@ -2234,11 +2237,15 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS)
     Capability *old_capabilities = NULL;
     uint32_t old_n_capabilities = n_capabilities;
 
+    if (RELAXED_LOAD(&concurrent_coll_running)) {
+        return 1;
+    }
+
     if (new_n_capabilities == enabled_capabilities) {
-        return;
+        return 0;
     } else if (new_n_capabilities <= 0) {
         errorBelch("setNumCapabilities: Capability count must be positive");
-        return;
+        return 1;
     }
 
 
@@ -2340,6 +2347,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS)
 
     rts_unlock(cap);
 
+    return 0;
 #endif // THREADED_RTS
 }
 


=====================================
rts/include/rts/Threads.h
=====================================
@@ -85,4 +85,4 @@ extern Capability MainCapability;
 // Change the number of capabilities (only supports increasing the
 // current value at the moment).
 //
-extern void setNumCapabilities (uint32_t new_);
+extern int setNumCapabilities (uint32_t new_);


=====================================
rts/sm/NonMoving.h
=====================================
@@ -344,7 +344,7 @@ INLINE_HEADER bool nonmovingClosureBeingSwept(StgClosure *p)
 
 INLINE_HEADER bool isNonmovingClosure(StgClosure *p)
 {
-    return !HEAP_ALLOCED_GC(p) || Bdescr((P_)p)->flags & BF_NONMOVING;
+    return RtsFlags.GcFlags.useNonmoving && (!HEAP_ALLOCED_GC(p) || Bdescr((P_)p)->flags & BF_NONMOVING);
 }
 
 #if defined(DEBUG)


=====================================
rts/sm/NonMovingMark.c
=====================================
@@ -1319,8 +1319,11 @@ mark_closure (MarkQueue *queue, const StgClosure *p0, StgClosure **origin)
             goto done;
 
         case WHITEHOLE:
-            while (*(StgInfoTable* volatile*) &p->header.info == &stg_WHITEHOLE_info);
-                // busy_wait_nop(); // FIXME
+            while (*(StgInfoTable* volatile*) &p->header.info == &stg_WHITEHOLE_info)
+#if defined(PARALLEL_GC)
+                busy_wait_nop()
+#endif
+                ;
             goto try_again;
 
         default:
@@ -1599,7 +1602,7 @@ mark_closure (MarkQueue *queue, const StgClosure *p0, StgClosure **origin)
         // selectee unreachable. However, we must mark the selectee regardless
         // to satisfy the snapshot invariant.
         PUSH_FIELD(sel, selectee);
-        nonmoving_eval_thunk_selector(queue, sel, origin);
+        //nonmoving_eval_thunk_selector(queue, sel, origin);
         break;
     }
 


=====================================
rts/sm/NonMovingShortcut.c
=====================================
@@ -42,7 +42,7 @@ update_selector_chain(
 ) {
     ASSERT(val != NULL);
 
-    // Make sure we don't introduce non-moving-to-moving pointers here.
+    // Make sure we don't introduce nonmoving-to-moving pointers here.
     ASSERT(isNonmovingClosure(val));
 
     // This case we can't handle because we don't know info ptr of the closure



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/f095454b5bcf0d604e62c784931f80b5d7f0fb88...8ce0eb1fc8563838fe6b6ec151eedba395a2e0d1

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/f095454b5bcf0d604e62c784931f80b5d7f0fb88...8ce0eb1fc8563838fe6b6ec151eedba395a2e0d1
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