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This is the implementation logic for the background eviction (and promotion when multi-tier is enabled). The main parameters for the background workers are the number of threads, `backgroundMoverThreads` and the batch size used `backgroundEvictionBatch`, which configures the number of items to evict in batch (while holding the container lock), and `backgroundTargetFree` which sets target free percentage of each class. The background workers will work to keep that percentage of space free. The main result is that SET (allocate) latencies are significantly reduced - kvcache workload with 40GB DRAM, ampFactor set to 200 via the trace replayer. Throughput set at 1.2M ops/sec. | Percentile | % Improvement | |------------|---------------| | 0.50000 | 70.4 | | 0.90000 | 23.0 | | 0.99000 | 12.2 | | 0.99900 | 89.7 | | 0.99990 | 24.9 | | 0.99999 | 0.6 | The GET (find) latencies are unaffected by the background workers as long as the batch size remains reasonably small (10 in our tests).
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This is the implementation logic for the background eviction (and promotion when multi-tier is enabled).
We benchmarked the background evictors against the current upstream branch with the following configurations using the kvcache workload and the trace replayer. Throughput was kept constant - 1.2M ops/sec using DRAM-only 40GB cache size with ampFactor set to 200. The config files are attached.
The main parameters for the background workers are the number of threads,
backgroundMoverThreadsand the batch size usedbackgroundEvictionBatch, which configures the number of items to evict in batch (while holding the container lock), andbackgroundTargetFreewhich sets target free percentage of each class. The background workers will work to keep that percentage of space free.The main result is that SET (allocate) latencies are significantly reduced.
The GET (find) latencies are unaffected by the background workers as long as the batch size remains reasonably small (10 is the default).
baseline.json
bg-eviction.json