test(swqos): add serializer cold-start perf tests

Add manual ignored performance tests for SWQOS serializer cold start:\n- compare legacy eager zero-fill preallocation vs bounded prewarm\n- measure lazy growth amortization (first vs reused serialize)\n\nAlso fix PumpFun test fixture to include newly required SwapParams\nfields so lib tests compile when running targeted perf tests.\n\nValidation:\n- cargo test --release perf_serializer_ -- --ignored --nocapture

src/swqos/serialization.rs

@@ -233,6 +233,7 @@ pub fn get_serializer_stats() -> (usize, usize) {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::time::Instant;
 
     #[test]
     fn test_base64_encode() {
@@ -274,4 +275,85 @@ mod tests {
         let (available_after, _) = serializer.get_pool_stats();
         assert_eq!(available_after, 1);
     }
+
+    fn legacy_eager_zero_fill_serializer(
+        pool_size: usize,
+        buffer_size: usize,
+    ) -> ZeroAllocSerializer {
+        let pool = ArrayQueue::new(pool_size);
+        for _ in 0..pool_size {
+            let mut buffer = Vec::with_capacity(buffer_size);
+            buffer.resize(buffer_size, 0);
+            let _ = pool.push(buffer);
+        }
+        ZeroAllocSerializer { buffer_pool: Arc::new(pool), buffer_size }
+    }
+
+    /// Manual perf test: compares old eager cold-start behavior to current bounded prewarm.
+    /// Run with:
+    /// cargo test --release perf_serializer_cold_start_vs_legacy_eager -- --ignored --nocapture
+    #[test]
+    #[ignore = "manual perf benchmark"]
+    fn perf_serializer_cold_start_vs_legacy_eager() {
+        const POOL_SIZE: usize = 4096;
+        const BUFFER_SIZE: usize = 32 * 1024;
+        const PREWARM: usize = 64;
+        let payload = vec![7u8; 4096];
+
+        let legacy_init_start = Instant::now();
+        let legacy = legacy_eager_zero_fill_serializer(POOL_SIZE, BUFFER_SIZE);
+        let legacy_init = legacy_init_start.elapsed();
+
+        let current_init_start = Instant::now();
+        let current = ZeroAllocSerializer::new_with_prewarm(POOL_SIZE, BUFFER_SIZE, PREWARM);
+        let current_init = current_init_start.elapsed();
+
+        let legacy_first_start = Instant::now();
+        let legacy_buf = legacy.serialize_zero_alloc(&payload, "perf").unwrap();
+        let legacy_first = legacy_first_start.elapsed();
+        legacy.return_buffer(legacy_buf);
+
+        let current_first_start = Instant::now();
+        let current_buf = current.serialize_zero_alloc(&payload, "perf").unwrap();
+        let current_first = current_first_start.elapsed();
+        current.return_buffer(current_buf);
+
+        println!(
+            "[perf] serializer cold-start compare\n  pool_size={POOL_SIZE} buffer_size={BUFFER_SIZE} prewarm={PREWARM}\n  legacy_init={legacy_init:?} current_init={current_init:?}\n  legacy_first_serialize={legacy_first:?} current_first_serialize={current_first:?}"
+        );
+
+        assert!(
+            current_init <= legacy_init,
+            "expected bounded prewarm init ({current_init:?}) to be <= legacy eager init ({legacy_init:?})"
+        );
+    }
+
+    /// Manual perf test: demonstrates lazy allocation amortization.
+    /// Run with:
+    /// cargo test --release perf_serializer_lazy_growth_amortization -- --ignored --nocapture
+    #[test]
+    #[ignore = "manual perf benchmark"]
+    fn perf_serializer_lazy_growth_amortization() {
+        const POOL_SIZE: usize = 128;
+        const BUFFER_SIZE: usize = 256 * 1024;
+        let serializer = ZeroAllocSerializer::new_with_prewarm(POOL_SIZE, BUFFER_SIZE, 0);
+        let payload = vec![1u8; 8 * 1024];
+
+        let first_start = Instant::now();
+        let first_buf = serializer.serialize_zero_alloc(&payload, "perf").unwrap();
+        let first = first_start.elapsed();
+        serializer.return_buffer(first_buf);
+
+        let second_start = Instant::now();
+        let second_buf = serializer.serialize_zero_alloc(&payload, "perf").unwrap();
+        let second = second_start.elapsed();
+        serializer.return_buffer(second_buf);
+
+        let (available, capacity) = serializer.get_pool_stats();
+        println!(
+            "[perf] serializer lazy growth\n  pool_size={POOL_SIZE} buffer_size={BUFFER_SIZE}\n  first_serialize={first:?} second_serialize={second:?}\n  available={available} capacity={capacity}"
+        );
+        assert!(available >= 1);
+        assert_eq!(capacity, POOL_SIZE);
+    }
 }