mikemccand commented on PR #15779:
URL: https://github.com/apache/lucene/pull/15779#issuecomment-3997375712

   > Yes, but this is actually same as the access below.
   
   Well, you're putting 2X pressure on the cache lines right?  (Both 
sequential).  1) Is stepping through `bytesStart` array, 2) is reading from a 
different spot in virtual address space (current 32 KB `byte[]` holding the 
`byte[]` key for each entry?
   
   Whereas if you only stepped through the pages directly that's a single 
sequential read stream.  But, it's an added 1 or 2 byte `vInt` decode, yet, 
that `if` should be trivial for CPU (almost always 1 byte, keys < 128 length 
vast majority of time).
   
   I'm not sure which would be better!  This mechanical / physics sympathy is 
hard for me to model/predict...
   
   So these 1 or 2 sequential read streams then also wrestle with the 
random-access writes we do into the new hash `ids` array.


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