[Git][ghc/ghc][wip/T18043] rts: Flush eventlog buffers from flushEventLog

[Ben Gamari]

Ben Gamari pushed to branch wip/T18043 at Glasgow Haskell Compiler / GHC


Commits:
2c9c830d by Ben Gamari at 2020-04-11T20:23:33-04:00
rts: Flush eventlog buffers from flushEventLog

As noted in #18043, flushTrace failed flush anything beyond the writer.
This means that a significant amount of data sitting in capability-local
event buffers may never get flushed, despite the users' pleads for us to
flush.

Fix this by making flushEventLog flush all of the event buffers before
flushing the writer.

Fixes #18043.

- - - - -


10 changed files:

- includes/RtsAPI.h
- includes/rts/EventLogWriter.h
- libraries/base/Debug/Trace.hs
- rts/Capability.c
- rts/Capability.h
- rts/Schedule.c
- rts/Trace.c
- rts/Trace.h
- rts/eventlog/EventLog.c
- rts/eventlog/EventLog.h


Changes:

=====================================
includes/RtsAPI.h
=====================================
@@ -17,7 +17,6 @@ extern "C" {
 
 #include "HsFFI.h"
 #include "rts/Time.h"
-#include "rts/EventLogWriter.h"
 
 /*
  * Running the scheduler
@@ -47,6 +46,9 @@ typedef struct CapabilityPublic_ {
     StgRegTable r;
 } CapabilityPublic;
 
+/* N.B. this needs the Capability declaration above. */
+#include "rts/EventLogWriter.h"
+
 /* ----------------------------------------------------------------------------
    RTS configuration settings, for passing to hs_init_ghc()
    ------------------------------------------------------------------------- */


=====================================
includes/rts/EventLogWriter.h
=====================================
@@ -64,3 +64,8 @@ bool startEventLogging(const EventLogWriter *writer);
  * Stop event logging and destroy the current EventLogWriter.
  */
 void endEventLogging(void);
+
+/*
+ * Flush the eventlog. cap can be NULL if one is not held.
+ */
+void flushEventLog(Capability **cap);


=====================================
libraries/base/Debug/Trace.hs
=====================================
@@ -37,6 +37,7 @@ module Debug.Trace (
         -- $eventlog_tracing
         traceEvent,
         traceEventIO,
+        flushEventLog,
 
         -- * Execution phase markers
         -- $markers
@@ -319,3 +320,11 @@ traceMarkerIO :: String -> IO ()
 traceMarkerIO msg =
   GHC.Foreign.withCString utf8 msg $ \(Ptr p) -> IO $ \s ->
     case traceMarker# p s of s' -> (# s', () #)
+
+-- | Immediately flush the event log, if enabled.
+--
+-- @since 4.15.0.0
+flushEventLog :: IO ()
+flushEventLog = c_flushEventLog nullPtr
+
+foreign import ccall "flushEventLog" c_flushEventLog :: Ptr () -> IO ()


=====================================
rts/Capability.c
=====================================
@@ -885,6 +885,10 @@ yieldCapability (Capability** pCap, Task *task, bool gcAllowed)
                 debugTrace(DEBUG_nonmoving_gc, "Flushing update remembered set blocks...");
                 break;
 
+            case SYNC_FLUSH_EVENT_LOG:
+                flushLocalEventsBuf(cap);
+                break;
+
             default:
                 break;
             }


=====================================
rts/Capability.h
=====================================
@@ -263,7 +263,8 @@ typedef enum {
     SYNC_OTHER,
     SYNC_GC_SEQ,
     SYNC_GC_PAR,
-    SYNC_FLUSH_UPD_REM_SET
+    SYNC_FLUSH_UPD_REM_SET,
+    SYNC_FLUSH_EVENT_LOG
 } SyncType;
 
 //


=====================================
rts/Schedule.c
=====================================
@@ -2035,7 +2035,7 @@ forkProcess(HsStablePtr *entry
     stopTimer(); // See #4074
 
 #if defined(TRACING)
-    flushEventLog(); // so that child won't inherit dirty file buffers
+    flushTrace(); // so that child won't inherit dirty file buffers
 #endif
 
     pid = fork();


=====================================
rts/Trace.c
=====================================
@@ -117,10 +117,10 @@ void resetTracing (void)
     restartEventLogging();
 }
 
-void flushTrace (void)
+void flushTrace ()
 {
     if (eventlog_enabled) {
-        flushEventLog();
+        flushEventLog(NULL);
     }
 }
 


=====================================
rts/Trace.h
=====================================
@@ -319,7 +319,6 @@ void traceConcSweepEnd(void);
 void traceConcUpdRemSetFlush(Capability *cap);
 void traceNonmovingHeapCensus(uint32_t log_blk_size,
                               const struct NonmovingAllocCensus *census);
-
 void flushTrace(void);
 
 #else /* !TRACING */


=====================================
rts/eventlog/EventLog.c
=====================================
@@ -16,6 +16,7 @@
 #include "RtsUtils.h"
 #include "Stats.h"
 #include "EventLog.h"
+#include "Schedule.h"
 
 #include <string.h>
 #include <stdio.h>
@@ -271,7 +272,7 @@ stopEventLogWriter(void)
 }
 
 void
-flushEventLog(void)
+flushEventLogWriter(void)
 {
     if (event_log_writer != NULL &&
             event_log_writer->flushEventLog != NULL) {
@@ -1565,6 +1566,26 @@ void postEventType(EventsBuf *eb, EventType *et)
     postInt32(eb, EVENT_ET_END);
 }
 
+void flushLocalEventsBuf(Capability *cap)
+{
+    EventsBuf *eb = &capEventBuf[cap->no];
+    printAndClearEventBuf(eb);
+}
+
+void flushEventLog(Capability **cap USED_IF_THREADS)
+{
+    ACQUIRE_LOCK(&eventBufMutex);
+    printAndClearEventBuf(&eventBuf);
+    RELEASE_LOCK(&eventBufMutex);
+
+#if defined(THREADED_RTS)
+    Task *task = myTask();
+    stopAllCapabilitiesWith(cap, task, SYNC_FLUSH_EVENT_LOG);
+    releaseAllCapabilities(n_capabilities, cap ? *cap : NULL, task);
+#endif
+    flushEventLogWriter();
+}
+
 #else
 
 enum EventLogStatus eventLogStatus(void)
@@ -1578,4 +1599,6 @@ bool startEventLogging(const EventLogWriter *writer STG_UNUSED) {
 
 void endEventLogging(void) {}
 
+void flushEventLog(Capability **cap STG_UNUSED) {}
+
 #endif /* TRACING */


=====================================
rts/eventlog/EventLog.h
=====================================
@@ -28,8 +28,10 @@ void initEventLogging(void);
 void restartEventLogging(void);
 void freeEventLogging(void);
 void abortEventLogging(void); // #4512 - after fork child needs to abort
-void flushEventLog(void);     // event log inherited from parent
+void flushEventLogWriter(void);     // event log inherited from parent
 void moreCapEventBufs (uint32_t from, uint32_t to);
+void flushLocalEventsBuf(Capability *cap);
+void flushAllEventsBufs(Capability *cap);
 
 /*
  * Post a scheduler event to the capability's event buffer (an event



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/2c9c830d58e41df4e74e1eea936e344805ff88ad

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/2c9c830d58e41df4e74e1eea936e344805ff88ad
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