Clear lastProcessedAckEvents in same loop
Clear lastProcessedAckEvents in same loop

Summary: Deferring it to the next read causes a bunch of data to go out of cache, which guarantees a cache miss when we try to clear it. Instead, clear it immediately after the callbacks.

Reviewed By: bschlinker

Differential Revision: D36151205

fbshipit-source-id: 467a45e2ef901b5705fb3db38d2648ba97784c8d

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