Solutions within vLLM community (source) to address the ever expanding problem of very high cost of GPU compute for having to recompute the previous prompts.
PagedAttention
-Core innovation in vLLM
- Manages KV cache in blocks/pages
- Enables efficient memory management
- Reduces memory fragmentation
- Allows dynamic allocation/deallocation
Continuous Batching
- Dynamic batching of incoming requests
- Efficient scheduling of compute resources
- Reduces idle GPU time
- Optimizes throughput without sacrificing latency
Block-Sparse Attention
def block_sparse_attention(query, key, value, block_size):
# Divide attention computation into blocks
blocks = divide_into_blocks(query, key, value, block_size)
# Compute attention only for relevant blocks
sparse_attention = compute_sparse_blocks(blocks)
return sparse_attention
Cache Management Strategies
- LRU (Least Recently Used) cache eviction
- Priority-based cache management
- Dynamic cache sizing
- Intelligent prefetching
Pipeline Parallelism
- Distributing computation across multiple GPUs
- Efficient load balancing
- Reduced memory pressure per device
- Optimized inter-GPU communication
Implementation Optimizations
class KVCacheManager:
def __init__(self, cache_size, block_size):
self.cache = {}
self.lru = []
self.cache_size = cache_size
self.block_size = block_size
def add_to_cache(self, key, value):
if len(self.cache) >= self.cache_size:
# Evict least recently used
lru_key = self.lru.pop(0)
del self.cache[lru_key]
self.cache[key] = value
self.lru.append(key)
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