uschindler commented on issue #15079:
URL: https://github.com/apache/lucene/issues/15079#issuecomment-3214079390
Here is the example for a standard `MemorySegmentIndexInput#readByte()`:
```
0.38% 2071
jdk.internal.foreign.MemorySessionImpl#checkValidStateRaw() [Inlined code]
at
jdk.internal.misc.ScopedMemoryAccess#getByteInternal() [Inlined code]
at
jdk.internal.misc.ScopedMemoryAccess#getByte() [Inlined code]
at
java.lang.invoke.VarHandleSegmentAsBytes#get() [Inlined code]
at
java.lang.invoke.LambdaForm$DMH.0x00007ff76d191c00#invokeStatic() [Inlined code]
at
java.lang.invoke.LambdaForm$MH.0x00007ff76d193000#invoke() [Inlined code]
at
java.lang.invoke.VarHandleGuards#guard_LJ_I() [Inlined code]
at
jdk.internal.foreign.AbstractMemorySegmentImpl#get() [Inlined code]
at
org.apache.lucene.store.MemorySegmentIndexInput#readByte() [Inlined code]
at
org.apache.lucene.codecs.lucene103.PForUtil#decode() [JIT compiled code]
at
org.apache.lucene.codecs.lucene103.Lucene103PostingsReader$BlockPostingsEnum#refillPositions()
[JIT compiled code]
at
org.apache.lucene.codecs.lucene103.Lucene103PostingsReader$BlockPostingsEnum#nextPosition()
[Inlined code]
```
Here you see the Varhandle code is inlined. I have no idea why this does not
happen for the GroupVInt code. I have some ideas.
@easyice: Do you think we could change ReadGroupVintUtil to be an instance
class instead of purely static. The we could add a getter to IndexInput to
retrieve an instance for the given IndexInput that can read and decode
IndexInputs. All VarHandles and the delegate would be final fields in that
instance and therefor are better to inline.
I think the whole problem with the lambda and also those VarHandles here is
the fact that the JVM cannot assume them to be static (as the captures for the
lambda) and/or singletons (the VarHandle is static, but the delegate is passed
on each call).
The main problem of the current code is the "callback", i think we can
revisit this. Let me think about it a bit over the weekend.
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