Apparent regression in memory segment access in JDK 23?

[Chris Hegarty]

Hi,

I'm trying to track down what appears as a regression when accessing 
long values from a memory segment, when moving from JDK 22 to JDK 23. 
Approx 100-150% slower.

There are some details in this GH issue [1], but not a lot more than 
what is in this email.

I'm still debugging, but git bisect on JDK 23 builds was not all that 
helpful. I did see some changes in b25 and further in b26 (to restore a 
varhandle cache).

I'm still trying to get a basic jmh benchmark, but so far I've been 
unable to reproduce this yet. I'll keep trying

Any thoughts or comments would be gratefully appreciated.


JDK 23:
   @ 16 
org.apache.lucene.util.packed.DirectReader$DirectPackedReader40::get (34 
bytes)   inline (hot)
    \-> TypeProfile (11846/11846 counts) = 
org/apache/lucene/util/packed/DirectReader$DirectPackedReader40
    @ 14 
org.apache.lucene.store.MemorySegmentIndexInput$SingleSegmentImpl::readLong 
(31 bytes)   inline (hot)
      \-> TypeProfile (11494/11494 counts) = 
org/apache/lucene/store/MemorySegmentIndexInput$SingleSegmentImpl
       @ 8   jdk.internal.foreign.AbstractMemorySegmentImpl::get (12 
bytes)   force inline by annotation
        \-> TypeProfile (11022/11022 counts) = 
jdk/internal/foreign/MappedMemorySegmentImpl
         @ 1 
jdk.internal.foreign.layout.ValueLayouts$AbstractValueLayout::varHandle 
(43 bytes)   force inline by annotation
         @ 8   java.lang.invoke.VarHandleGuards::guard_LJ_J (84 bytes) 
force inline by annotation
           @ 3 
java.lang.invoke.IndirectVarHandle::checkAccessModeThenIsDirect (8 
bytes)   force inline by annotation
             @ 2 
java.lang.invoke.VarHandle::checkAccessModeThenIsDirect (29 bytes) 
force inline by annotation
           @ 59   java.lang.invoke.VarHandle::getMethodHandle (41 bytes) 
   force inline by annotation
           @ 71   java.lang.invoke.MethodHandle::asType (32 bytes) 
failed to inline: already compiled into a big method
           @ 75   java.lang.invoke.IndirectVarHandle::asDirect (5 bytes) 
   accessor
           @ 80   java.lang.invoke.MethodHandle::invokeBasic(LLJ)J (0 
bytes)   failed to inline: receiver not constant

JDK 22:
    @ 16 
org.apache.lucene.util.packed.DirectReader$DirectPackedReader40::get (34 
bytes)   inline (hot)
     \-> TypeProfile (6998/6998 counts) = 
org/apache/lucene/util/packed/DirectReader$DirectPackedReader40
      @ 14 
org.apache.lucene.store.MemorySegmentIndexInput$SingleSegmentImpl::readLong 
(31 bytes)   inline (hot)
       \-> TypeProfile (7475/7475 counts) = 
org/apache/lucene/store/MemorySegmentIndexInput$SingleSegmentImpl
        @ 8   jdk.internal.foreign.AbstractMemorySegmentImpl::get (12 
bytes)   force inline by annotation
         \-> TypeProfile (10270/10270 counts) = 
jdk/internal/foreign/MappedMemorySegmentImpl
          @ 1 
jdk.internal.foreign.layout.ValueLayouts$AbstractValueLayout::varHandle 
(26 bytes)   force inline by annotation
          @ 8   java.lang.invoke.VarHandleGuards::guard_LJ_J (84 bytes) 
  force inline by annotation
            @ 3 
java.lang.invoke.VarHandle::checkAccessModeThenIsDirect (29 bytes) 
force inline by annotation
            @ 46   java.lang.invoke.VarForm::getMemberName (38 bytes) 
force inline by annotation
            @ 49   java.lang.invoke.VarHandleSegmentAsLongs::get (52 
bytes)   force inline by annotation
              @ 14 
java.lang.invoke.VarHandleSegmentAsLongs::checkAddress (21 bytes) 
force inline by annotation
                @ 1   java.util.Objects::requireNonNull (14 bytes) 
force inline by annotation
                @ 15 
jdk.internal.foreign.AbstractMemorySegmentImpl::checkAccess (30 bytes) 
force inline by annotation
                  @ 26 
jdk.internal.foreign.AbstractMemorySegmentImpl::checkBounds (54 bytes) 
force inline by annotation
                    @ 16   jdk.internal.util.Preconditions::checkIndex 
(22 bytes)   (intrinsic)
              @ 24 
jdk.internal.foreign.AbstractMemorySegmentImpl::sessionImpl (5 bytes) 
accessor
              @ 29 
jdk.internal.foreign.NativeMemorySegmentImpl::unsafeGetBase (2 bytes) 
inline (hot)
              @ 40 
java.lang.invoke.VarHandleSegmentAsLongs::offsetPlain (39 bytes)   force 
inline by annotation
                @ 1 
jdk.internal.foreign.NativeMemorySegmentImpl::unsafeGetOffset (5 bytes) 
  accessor
                @ 13 
jdk.internal.foreign.NativeMemorySegmentImpl::maxAlignMask (2 bytes) 
inline (hot)
              @ 48 
jdk.internal.misc.ScopedMemoryAccess::getLongUnaligned (18 bytes) 
force inline by annotation
                @ 6 
jdk.internal.misc.ScopedMemoryAccess::getLongUnalignedInternal (36 
bytes)   force inline by annotation
                  @ 5 
jdk.internal.foreign.MemorySessionImpl::checkValidStateRaw (33 bytes) 
force inline by annotation
                  @ 15   jdk.internal.misc.Unsafe::getLongUnaligned (12 
bytes)   inline (hot)
                    @ 5   jdk.internal.misc.Unsafe::getLongUnaligned 
(173 bytes)   (intrinsic)
                    @ 8   jdk.internal.misc.Unsafe::convEndian (16 
bytes)   inline (hot)
                  @ 21   java.lang.ref.Reference::reachabilityFence (1 
bytes)   force inline by annotation

-Chris

[1] https://github.com/elastic/elasticsearch/issues/113030