Multi-tier CacheLib part 1 #356
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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 | | 0.95000 | 23.0 | | 0.99500 | 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).
This includes printing: - allocSize - allocated memory size - memory usage fraction
Part 1. ----------------------------------------- This includes the following: - Multi-tier allocator with TierId - allocateInternalTier - creating multi-tier allocator on shared memory - serialization - some basic tests - Add option to insert items to first free tier, this enables an interleaving approach. Ther is no data movement among the tiers. Use `insertToFirstFreeTier` option to control. In order to evict data from the second tier, you will need to have the background movers enabled.
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Initial multi-tier support implementation. This allows you to bind the cache to specified NUMA nodes where CXL memory can be exposed. The default behavior is to allocate to the first tier that has an open allocation. When the background workers are invoked, they proactively evict items from both tiers. Resulting an interleaving behavior since there is no data movement between the tiers in this part.
This includes the following:
an interleaving approach. Ther is no data movement among
the tiers. Use
insertToFirstFreeTieroption to control.In order to evict data from the second tier, you will need
to have the background movers enabled.