Basic test passes

router/src/infer/v3/block_allocator.rs

@@ -151,9 +151,11 @@ pub(crate) struct BlockAllocationWithCache {
 struct BlockState {
     block_id: u32,
     last_accessed: u64,
+    predecessor: Option<u64>,
     ref_count: usize,
 }
 
+#[derive(Debug)]
 pub struct PrefixCache {
     block_size: usize,
     cache_partial: bool,
@@ -180,10 +182,11 @@ impl PrefixCache {
         mut n_tokens: usize,
         prefill_tokens: &[u32],
     ) -> Option<BlockAllocationWithCache> {
-        // First try to lookup prefix.
         let mut hasher = DefaultHasher::new();
         let mut tokens_from_cache = 0;
         let mut cache_blocks_hashes = Vec::new();
+        let mut prefix_cache_blocks = Vec::new();
+        let mut prefix_hashes = Vec::new();
         for prefill_chunk in prefill_tokens.chunks(self.block_size) {
             if prefill_chunk.len() < self.block_size && !self.cache_partial {
                 break;
@@ -193,22 +196,28 @@ impl PrefixCache {
 
             match self.cache_blocks.get_mut(&hasher.finish()) {
                 Some(state) => {
+                    // Ensure that we don't evict the prefix blocks.
                     state.ref_count += 1;
+                    prefix_cache_blocks.push(state.block_id);
+                    prefix_hashes.push(hasher.finish());
                 }
-                None => todo!(),
+                None => break,
-            }
-
-            if !self.cache_blocks.contains_key(&hasher.finish()) {
-                break;
             }
 
             tokens_from_cache += prefill_chunk.len();
-            cache_blocks_hashes.push(hasher.finish());
         }
 
-        let blocks = self.alloc_or_reclaim(n_tokens - tokens_from_cache)?;
+        let blocks = match self.alloc_or_reclaim(n_tokens - tokens_from_cache) {
+            Some(blocks) => blocks,
+            None => {
+                prefix_hashes.into_iter().for_each(|hash| {
+                    self.cache_blocks.get_mut(&hash).unwrap().ref_count -= 1;
+                });
+
+                return None;
+            }
+        };
 
-        let mut prefix_cache_blocks = Vec::new();
         for hash in cache_blocks_hashes {
             match self.cache_blocks.get_mut(&hash) {
                 Some(info) => {
@@ -219,6 +228,9 @@ impl PrefixCache {
             }
         }
 
+        eprintln!("Allocated blocks: {:?}", blocks);
+        eprintln!("Prefix blocks: {:?}", prefix_cache_blocks);
+
         prefix_cache_blocks.extend(blocks);
 
         let mut slots = Vec::with_capacity(n_tokens);
@@ -279,7 +291,7 @@ impl PrefixCache {
 
     fn free(&mut self, blocks: &[u32], prefill_tokens: &[u32]) {
         let mut hasher = DefaultHasher::new();
-
+        let mut predecessor = None;
         for (prefill_chunk, block_id) in prefill_tokens.chunks(self.block_size).zip(blocks.iter()) {
             if prefill_chunk.len() < self.block_size && !self.cache_partial {
                 break;
@@ -298,13 +310,21 @@ impl PrefixCache {
                     entry.insert(BlockState {
                         block_id: *block_id,
                         last_accessed: self.time,
+                        predecessor,
                         ref_count: 0,
                     });
                 }
             };
+
+            predecessor = Some(hasher.finish());
         }
 
         self.time += 1;
+
+        let n_prefill_blocks = (prefill_tokens.len() + self.block_size - 1) / self.block_size;
+        for block in &blocks[n_prefill_blocks..] {
+            self.free_blocks.push(*block);
+        }
     }
 }
 
@@ -327,6 +347,8 @@ mod tests {
         );
         cache.free(&allocation.unwrap().blocks, &[0, 1, 2, 3]);
 
+        eprintln!("{:?}", cache);
+
         let allocation = cache.alloc(8, &[0, 1, 2, 3]);
         assert_eq!(
             allocation,