Force a upb_MiniTable and its fields to be contiguous in memory. #20160
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The default size for an empty arena is 256 bytes; if a minidescriptor is 20 bytes long, the arena will allocate another separate block for the minitable fields, which depending on the allocator could increase TLB pressure. I did try implementing this as a flexible array member on `upb_MiniTable`, but unfortunately that's already used for the fasttable members, and it actually inexplicably showed tiny perf regressions in parsing benchmarks. PiperOrigin-RevId: 720815985
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Force a upb_MiniTable and its fields to be contiguous in memory.
The default size for an empty arena is 256 bytes; if a minidescriptor is 20 bytes long, the arena will allocate another separate block for the minitable fields, which depending on the allocator could increase TLB pressure.
I did try implementing this as a flexible array member on
upb_MiniTable, but unfortunately that's already used for the fasttable members, and it actually inexplicably showed tiny perf regressions in parsing benchmarks.