Reduce the maximum grant possible we can store in the BBQueue

crates/milli/src/update/new/channel.rs

@@ -27,6 +27,12 @@ use crate::update::new::KvReaderFieldId;
 use crate::vector::Embedding;
 use crate::{CboRoaringBitmapCodec, DocumentId, Error, Index, InternalError};
 
+/// Note that the FrameProducer requires up to 9 bytes to
+/// encode the length, the max grant has been computed accordingly.
+///
+/// <https://docs.rs/bbqueue/latest/bbqueue/framed/index.html#frame-header>
+const MAX_FRAME_HEADER_SIZE: usize = 9;
+
 /// Creates a tuple of senders/receiver to be used by
 /// the extractors and the writer loop.
 ///
@@ -53,8 +59,8 @@ pub fn extractor_writer_bbqueue(
     bbbuffers.resize_with(current_num_threads, || BBBuffer::new(bbbuffer_capacity));
 
     let capacity = bbbuffers.first().unwrap().capacity();
-    // Read the field description to understand this
-    let capacity = capacity.checked_sub(9).unwrap();
+    // Read the const description to understand this
+    let max_grant = capacity.saturating_div(2).checked_sub(MAX_FRAME_HEADER_SIZE).unwrap();
 
     let producers = ThreadLocal::with_capacity(bbbuffers.len());
     let consumers = rayon::broadcast(|bi| {
@@ -65,7 +71,7 @@ pub fn extractor_writer_bbqueue(
     });
 
     let (sender, receiver) = flume::bounded(channel_capacity);
-    let sender = ExtractorBbqueueSender { sender, producers, capacity };
+    let sender = ExtractorBbqueueSender { sender, producers, max_grant };
     let receiver = WriterBbqueueReceiver {
         receiver,
         look_at_consumer: (0..consumers.len()).cycle(),
@@ -81,13 +87,10 @@ pub struct ExtractorBbqueueSender<'a> {
     /// A memory buffer, one by thread, is used to serialize
     /// the entries directly in this shared, lock-free space.
     producers: ThreadLocal<FullySend<RefCell<FrameProducer<'a>>>>,
-    /// The capacity of this frame producer, will never be able to store more than that.
-    ///
-    /// Note that the FrameProducer requires up to 9 bytes to encode the length,
-    /// the capacity has been shrunk accordingly.
-    ///
-    /// <https://docs.rs/bbqueue/latest/bbqueue/framed/index.html#frame-header>
-    capacity: usize,
+    /// The maximum frame grant that a producer can reserve.
+    /// It will never be able to store more than that as the
+    /// buffer cannot split data into two parts.
+    max_grant: usize,
 }
 
 pub struct WriterBbqueueReceiver<'a> {
@@ -443,14 +446,14 @@ impl<'b> ExtractorBbqueueSender<'b> {
     }
 
     fn delete_vector(&self, docid: DocumentId) -> crate::Result<()> {
-        let capacity = self.capacity;
+        let max_grant = self.max_grant;
         let refcell = self.producers.get().unwrap();
         let mut producer = refcell.0.borrow_mut_or_yield();
 
         let payload_header = EntryHeader::ArroyDeleteVector(ArroyDeleteVector { docid });
         let total_length = EntryHeader::total_delete_vector_size();
-        if total_length > capacity {
-            panic!("The entry is larger ({total_length} bytes) than the BBQueue capacity ({capacity} bytes)");
+        if total_length > max_grant {
+            panic!("The entry is larger ({total_length} bytes) than the BBQueue max grant ({max_grant} bytes)");
         }
 
         // Spin loop to have a frame the size we requested.
@@ -468,7 +471,7 @@ impl<'b> ExtractorBbqueueSender<'b> {
         embedder_id: u8,
         embeddings: &[Vec<f32>],
     ) -> crate::Result<()> {
-        let capacity = self.capacity;
+        let max_grant = self.max_grant;
         let refcell = self.producers.get().unwrap();
         let mut producer = refcell.0.borrow_mut_or_yield();
 
@@ -479,7 +482,7 @@ impl<'b> ExtractorBbqueueSender<'b> {
         let arroy_set_vector = ArroySetVectors { docid, embedder_id, _padding: [0; 3] };
         let payload_header = EntryHeader::ArroySetVectors(arroy_set_vector);
         let total_length = EntryHeader::total_set_vectors_size(embeddings.len(), dimensions);
-        if total_length > capacity {
+        if total_length > max_grant {
             let mut value_file = tempfile::tempfile().map(BufWriter::new)?;
             for embedding in embeddings {
                 let mut embedding_bytes = bytemuck::cast_slice(embedding);
@@ -540,14 +543,14 @@ impl<'b> ExtractorBbqueueSender<'b> {
     where
         F: FnOnce(&mut [u8], &mut [u8]) -> crate::Result<()>,
     {
-        let capacity = self.capacity;
+        let max_grant = self.max_grant;
         let refcell = self.producers.get().unwrap();
         let mut producer = refcell.0.borrow_mut_or_yield();
 
         let operation = DbOperation { database, key_length: Some(key_length) };
         let payload_header = EntryHeader::DbOperation(operation);
         let total_length = EntryHeader::total_key_value_size(key_length, value_length);
-        if total_length > capacity {
+        if total_length > max_grant {
             let mut key_buffer = vec![0; key_length.get() as usize].into_boxed_slice();
             let value_file = tempfile::tempfile()?;
             value_file.set_len(value_length.try_into().unwrap())?;
@@ -601,7 +604,7 @@ impl<'b> ExtractorBbqueueSender<'b> {
     where
         F: FnOnce(&mut [u8]) -> crate::Result<()>,
     {
-        let capacity = self.capacity;
+        let max_grant = self.max_grant;
         let refcell = self.producers.get().unwrap();
         let mut producer = refcell.0.borrow_mut_or_yield();
 
@@ -610,8 +613,8 @@ impl<'b> ExtractorBbqueueSender<'b> {
         let operation = DbOperation { database, key_length: None };
         let payload_header = EntryHeader::DbOperation(operation);
         let total_length = EntryHeader::total_key_size(key_length);
-        if total_length > capacity {
-            panic!("The entry is larger ({total_length} bytes) than the BBQueue capacity ({capacity} bytes)");
+        if total_length > max_grant {
+            panic!("The entry is larger ({total_length} bytes) than the BBQueue max grant ({max_grant} bytes)");
         }
 
         // Spin loop to have a frame the size we requested.