llama: Ensure KV cache is fully defragmented. #10873
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Sometimes the KV cache requires defragmentation even without triggering the threshold heuristic. In this case, decoding will not being able to find a KV cache slot. This is particularly difficult for the caller to handle if it happens in between ubatches. To avoid this, we should immediately trigger a defrag. In addition, a heavily fragmented cache can require more than max_moves to defragment. Currently, we stop when we hit the limit but this can leave a cache that still does not have adequate space even after defragmentation is triggered. Instead, we should do multiple batches of processing until everything is complete.
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Sometimes the KV cache requires defragmentation even without triggering the threshold heuristic. In this case, decoding will not being able to find a KV cache slot. This is particularly difficult for the caller to handle if it happens in between ubatches. To avoid this, we should immediately trigger a defrag.
In addition, a heavily fragmented cache can require more than max_moves to defragment. Currently, we stop when we hit the limit but this can leave a cache that still does not have adequate space even after defragmentation is triggered. Instead, we should do multiple batches of processing until everything is complete.