Refer to: https://github.com/valkey-io/valkey/issues/1141
This update refactors the defrag code to:
* Make the overall code more readable and maintainable
* Reduce latencies incurred during defrag processing
With this update, the defrag cycle time is reduced to 500us, with more
frequent cycles. This results in much more predictable latencies, with a
dramatic reduction in tail latencies.
(See https://github.com/valkey-io/valkey/issues/1141 for more complete
details.)
This update is focused mostly on the high-level processing, and does NOT
address lower level functions which aren't currently timebound (e.g.
`activeDefragSdsDict()`, and `moduleDefragGlobals()`). These are out of
scope for this update and left for a future update.
I fixed `kvstoreDictLUTDefrag` because it was using up to 7ms on a CME
single shard. See original github issue for performance details.
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Signed-off-by: Jim Brunner <brunnerj@amazon.com>
Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
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