src/share/vm/runtime/arguments.cpp

rev 10500 : [backport] Rework ClassUnloading* flags handling
rev 10502 : [backport] ClassUnloadingWithConcurrentMark should be opt-in with Shenandoah
rev 10516 : [backport] Disable UseFastJNIAccessors for Shenandoah
rev 10583 : [backport] TLAB sizing policy should converge faster with Shenandoah
rev 10588 : [backport] Check and ensure that Shenandoah-enabled compilations succeed
* * *
[backport] Filter out not compilable methods to avoid false assertion
rev 10589 : [backport] Purge support for ShenandoahConcurrentEvacCodeRoots and ShenandoahBarriersForConst
rev 10592 : [backport] Fix Minimal and Zero builds
rev 10638 : [backport] Remove NMethodSizeLimit adjustment for Shenandoah

*** 1832,1841 ****
--- 1832,1877 ----
      if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
        warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
      }
      FLAG_SET_DEFAULT(ShenandoahUncommit, false);
    }
+ 
+   // If class unloading is disabled, no unloading for concurrent cycles as well.
+   // If class unloading is enabled, users should opt-in for unloading during
+   // concurrent cycles.
+   if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
+     if (PrintGC) {
+       tty->print_cr("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
+                     "are observed on class-unloading sensitive workloads");
+     }
+     FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
+   }
+ 
+   // JNI fast get field stuff is not currently supported by Shenandoah.
+   // It would introduce another heap memory access for reading the forwarding
+   // pointer, which would have to be guarded by the signal handler machinery.
+   // See:
+   // http://mail.openjdk.java.net/pipermail/hotspot-dev/2018-June/032763.html
+   FLAG_SET_DEFAULT(UseFastJNIAccessors, false);
+ 
+   // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
+   // historical data, assigning more recent data the weight according to TLABAllocationWeight.
+   // Current default is good for generational collectors that run frequent young GCs.
+   // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
+   // to converge faster over smaller number of resizing decisions.
+   if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
+     FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
+   }
+ 
+   // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
+   // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
+ #ifdef COMPILER2
+   if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
+     FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
+     FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
+   }
+ #endif
  #endif
  }
  
  #if !INCLUDE_ALL_GCS
  #ifdef ASSERT
*** 2156,2184 ****
    if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
      FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
    }
  
  #if INCLUDE_ALL_GCS
-   if (ShenandoahConcurrentEvacCodeRoots) {
-     if (!ShenandoahBarriersForConst) {
-       if (FLAG_IS_DEFAULT(ShenandoahBarriersForConst)) {
-         warning("Concurrent code cache evacuation is enabled, enabling barriers for constants.");
-         FLAG_SET_DEFAULT(ShenandoahBarriersForConst, true);
-       } else {
-         warning("Concurrent code cache evacuation is enabled, but barriers for constants are disabled. "
-                 "This may lead to surprising crashes.");
-       }
-     }
-   } else {
-     if (ShenandoahBarriersForConst) {
-       if (FLAG_IS_DEFAULT(ShenandoahBarriersForConst)) {
-         warning("Concurrent code cache evacuation is disabled, disabling barriers for constants.");
-         FLAG_SET_DEFAULT(ShenandoahBarriersForConst, false);
-       }
-     }
-   }
- 
    if (AlwaysPreTouch || ShenandoahAlwaysPreTouch) {
      if (!FLAG_IS_DEFAULT(ShenandoahUncommitDelay)) {
        warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommitDelay");
      }
      FLAG_SET_DEFAULT(ShenandoahUncommitDelay, max_uintx);
--- 2192,2201 ----