fix windowing

router/src/infer/v3/block_allocator.rs

@@ -24,6 +24,9 @@ impl BlockAllocation {
         &self.allocated_slots
     }
 
+    /// Extend an allocation by adding a new block
+    /// If the allocation length > window size, repeats blocks and slots to cover the
+    /// whole `required_blocks` and `required_slots`
     pub(crate) fn extend(&mut self) -> Result<(), AllocationError> {
         let (block, slots) = self.block_allocator.allocate_block()?;
         // Add block and slots to current allocation
@@ -48,6 +51,7 @@ impl BlockAllocation {
 }
 
 impl Drop for BlockAllocation {
+    /// Free the blocks
     fn drop(&mut self) {
         let allocated_blocks = std::mem::take(&mut self.allocated_blocks);
         self.block_allocator.free(allocated_blocks)
@@ -114,66 +118,71 @@ impl BlockAllocator {
         let required_prompt_blocks = (prompt_tokens + self.block_size - 1) / self.block_size;
         // prompt blocks + a single block for decode
         let required_blocks = required_prompt_blocks + 1;
+        let required_slots = required_blocks * self.block_size;
+
+        // Slots and blocks required for the whole request
+        let total_slots = prompt_tokens + decode_tokens;
+        let total_required_blocks = (total_slots + self.block_size - 1) / self.block_size;
 
         let (clipped_required_blocks, repeats) = match self.window_size {
-            // Nothing to do
-            None => (required_blocks, 1),
-            Some(window_size) => {
+            Some(window_size) if required_slots >= window_size => {
                 // Number of blocks for this window size
                 let window_size_blocks = (window_size + self.block_size - 1) / self.block_size;
-
-                if required_blocks > window_size_blocks {
-                    // Number of times we will need to repeat blocks to cover the required allocation
-                    let repeats = (required_blocks + window_size_blocks - 1) / window_size_blocks;
-                    (window_size_blocks, repeats)
-                } else {
-                    (required_blocks, 1)
-                }
+                // Number of times we will need to repeat blocks to cover the total allocation
+                let repeats = (total_slots + window_size - 1) / window_size;
+                (window_size_blocks, repeats)
             }
+            // Nothing to do
+            _ => (required_blocks, 1),
+        };
+
+        // Scoped to drop the lock early
+        let allocated_blocks = {
+            let mut free_blocks = self.free_blocks.lock().expect("Lock could not be acquired");
+            let clipped_required_blocks = clipped_required_blocks as usize;
+
+            if clipped_required_blocks > free_blocks.len() {
+                // Not enough blocks to cover this allocation
+                // Early return
+                return Err(AllocationError::NotEnoughPages);
+            }
+
+            // Take the blocks
+            let n_free_blocks = free_blocks.len();
+            free_blocks.split_off(n_free_blocks - clipped_required_blocks)
         };
 
         let repeats = repeats as usize;
-        let required_blocks = required_blocks as usize;
-        let clipped_required_blocks = clipped_required_blocks as usize;
+        let total_slots = total_slots as usize;
+        let total_required_blocks = total_required_blocks as usize;
 
-        let mut free_blocks = self.free_blocks.lock().expect("Lock could not be acquired");
-
-        if clipped_required_blocks > free_blocks.len() {
-            Err(AllocationError::NotEnoughPages)
+        let allocated_blocks = if repeats != 1 {
+            let mut allocated_blocks = allocated_blocks.repeat(repeats);
+            allocated_blocks.truncate(total_required_blocks);
+            allocated_blocks
         } else {
-            let n_free_blocks = free_blocks.len();
-            let allocated_blocks = free_blocks.split_off(n_free_blocks - clipped_required_blocks);
+            allocated_blocks
+        };
 
-            let allocated_blocks = if repeats != 1 {
-                let mut allocated_blocks = allocated_blocks.repeat(repeats);
-                allocated_blocks.truncate(required_blocks);
-                allocated_blocks
-            } else {
-                allocated_blocks
-            };
+        let mut allocated_slots =
+            Vec::with_capacity(allocated_blocks.len() * self.block_size as usize * repeats);
 
-            let mut allocated_slots =
-                Vec::with_capacity(allocated_blocks.len() * self.block_size as usize * repeats);
-
-            let required_slots = (prompt_tokens + decode_tokens) as usize;
-
-            'slots: for block_id in allocated_blocks.iter() {
-                for s in (block_id * self.block_size)..((block_id + 1) * self.block_size) {
-                    allocated_slots.push(s);
-                    if allocated_slots.len() > required_slots {
-                        break 'slots;
-                    }
+        'slots: for block_id in allocated_blocks.iter() {
+            for s in (block_id * self.block_size)..((block_id + 1) * self.block_size) {
+                allocated_slots.push(s);
+                if allocated_slots.len() > total_slots {
+                    break 'slots;
                 }
             }
-
-            Ok(BlockAllocation {
-                allocated_blocks,
-                allocated_slots,
-                required_blocks,
-                required_slots,
-                block_allocator: self.clone(),
-            })
         }
+
+        Ok(BlockAllocation {
+            allocated_blocks,
+            allocated_slots,
+            required_blocks: total_required_blocks,
+            required_slots: total_slots,
+            block_allocator: self.clone(),
+        })
     }
 
     pub(crate) fn free(&self, blocks: Vec<u32>) {

router/src/infer/v3/scheduler.rs

@@ -361,6 +361,7 @@ async fn decode(
 }
 
 /// Filter a `batch` and remove all requests not present in `entries`
+/// Ask the server to generate the full texts for entries in `terminated_entries`
 #[instrument(skip_all)]
 async fn filter_batch(
     client: &mut ShardedClient,
@@ -408,7 +409,10 @@ async fn filter_batch(
     }
 }
 
-///
+/// Send `InferStreamResponse::Intermediate` and the final `InferStreamResponse::End` messages
+/// to terminated requests
+/// It modifies the last `InferStreamResponse::Intermediate` to add the final full text in
+/// `terminated_generations`
 #[instrument(skip_all)]
 fn send_terminated_generations(
     terminated_generations: Vec<TerminatedGeneration>,
@@ -530,7 +534,7 @@ fn send_stream_responses(
 }
 
 /// Check if block allocations need to be extended
-/// If we don't have enough blocks, request will be filtered with be added to an IntMap of
+/// If we don't have enough blocks, request will be filtered and added to an IntMap of
 /// terminated entries.
 /// If at least one entry allocation was extended, we return true to force an update
 #[instrument(skip_all)]
@@ -592,6 +596,7 @@ fn filter_send_update_allocations(
 }
 
 /// Map `Generation` to `<(bool, Vec<(u64, InferStreamResponse)>)>`
+/// `bool` is `true` if the generation is finished
 fn map_generation(generation: Generation, entry: &Entry) -> (bool, Vec<InferStreamResponse>) {
     let mut finished = false;
     let mut stream_responses = Vec::with_capacity(16);