Allow customizing number of buffers

crates/buffet/src/bufpool.rs

@@ -19,7 +19,20 @@ pub fn initialize_allocator() -> Result<()> {
     #[cfg(feature = "miri")]
     let default_num_bufs = 1024;
 
-    initialize_allocator_with_num_bufs(default_num_bufs)
+    let mut num_bufs = default_num_bufs;
+
+    if let Ok(env_num_bufs) = std::env::var("BUFFET_NUM_BUFS") {
+        if let Ok(parsed_num_bufs) = env_num_bufs.parse::<usize>() {
+            num_bufs = parsed_num_bufs;
+        }
+    }
+
+    let mem_usage_in_mb: f64 = num_bufs as f64 * (BUF_SIZE as usize) as f64 / 1024.0 / 1024.0;
+    eprintln!(
+        "===== Initializing buffer pool with {} buffers, will use {:.2} MiB (override with $BUFFET_NUM_BUFS)",
+        num_bufs, mem_usage_in_mb
+    );
+    initialize_allocator_with_num_bufs(default_num_bufs as _)
 }
 
 impl BufMut {