diff --git a/src/common/buf.rs b/src/common/buf.rs
index d00071551b..ed4a5d7574 100644
--- a/src/common/buf.rs
+++ b/src/common/buf.rs
@@ -5,18 +5,21 @@ use bytes::{Buf, BufMut, Bytes, BytesMut};
 
 pub(crate) struct BufList<T> {
     bufs: VecDeque<T>,
+    remaining: usize,
 }
 
 impl<T: Buf> BufList<T> {
     pub(crate) fn new() -> BufList<T> {
         BufList {
             bufs: VecDeque::new(),
+            remaining: 0,
         }
     }
 
     #[inline]
     pub(crate) fn push(&mut self, buf: T) {
         debug_assert!(buf.has_remaining());
+        self.remaining += buf.remaining();
         self.bufs.push_back(buf);
     }
 
@@ -29,7 +32,7 @@ impl<T: Buf> BufList<T> {
 impl<T: Buf> Buf for BufList<T> {
     #[inline]
     fn remaining(&self) -> usize {
-        self.bufs.iter().map(|buf| buf.remaining()).sum()
+        self.remaining
     }
 
     #[inline]
@@ -39,6 +42,7 @@ impl<T: Buf> Buf for BufList<T> {
 
     #[inline]
     fn advance(&mut self, mut cnt: usize) {
+        self.remaining -= cnt;
         while cnt > 0 {
             {
                 let front = &mut self.bufs[0];
@@ -78,12 +82,18 @@ impl<T: Buf> Buf for BufList<T> {
             Some(front) if front.remaining() == len => {
                 let b = front.copy_to_bytes(len);
                 self.bufs.pop_front();
+                self.remaining -= len;
                 b
             }
-            Some(front) if front.remaining() > len => front.copy_to_bytes(len),
+            Some(front) if front.remaining() > len => {
+                self.remaining -= len;
+                front.copy_to_bytes(len)
+            }
             _ => {
-                assert!(len <= self.remaining(), "`len` greater than remaining");
+                assert!(len <= self.remaining, "`len` greater than remaining");
                 let mut bm = BytesMut::with_capacity(len);
+                // Note: `self.take(len)` calls `self.advance()` internally,
+                // which already decrements `self.remaining`.
                 bm.put(self.take(len));
                 bm.freeze()
             }
@@ -100,6 +110,7 @@ mod tests {
     fn hello_world_buf() -> BufList<Bytes> {
         BufList {
             bufs: vec![Bytes::from("Hello"), Bytes::from(" "), Bytes::from("World")].into(),
+            remaining: 11,
         }
     }
 
diff --git a/src/proto/h1/conn.rs b/src/proto/h1/conn.rs
index 3d71ed5bc5..94b2844538 100644
--- a/src/proto/h1/conn.rs
+++ b/src/proto/h1/conn.rs
@@ -239,7 +239,7 @@ where
             ParseContext {
                 cached_headers: &mut self.state.cached_headers,
                 req_method: &mut self.state.method,
-                h1_parser_config: self.state.h1_parser_config.clone(),
+                h1_parser_config: &self.state.h1_parser_config,
                 h1_max_headers: self.state.h1_max_headers,
                 preserve_header_case: self.state.preserve_header_case,
                 #[cfg(feature = "ffi")]
diff --git a/src/proto/h1/io.rs b/src/proto/h1/io.rs
index 6a30d73c84..de3a8eb4ff 100644
--- a/src/proto/h1/io.rs
+++ b/src/proto/h1/io.rs
@@ -68,7 +68,7 @@ where
             io,
             partial_len: None,
             read_blocked: false,
-            read_buf: BytesMut::with_capacity(0),
+            read_buf: BytesMut::with_capacity(INIT_BUFFER_SIZE),
             read_buf_strategy: ReadStrategy::default(),
             write_buf,
         }
@@ -182,7 +182,7 @@ where
                 ParseContext {
                     cached_headers: parse_ctx.cached_headers,
                     req_method: parse_ctx.req_method,
-                    h1_parser_config: parse_ctx.h1_parser_config.clone(),
+                    h1_parser_config: parse_ctx.h1_parser_config,
                     h1_max_headers: parse_ctx.h1_max_headers,
                     preserve_header_case: parse_ctx.preserve_header_case,
                     #[cfg(feature = "ffi")]
@@ -704,7 +704,7 @@ mod tests {
             let parse_ctx = ParseContext {
                 cached_headers: &mut None,
                 req_method: &mut None,
-                h1_parser_config: Default::default(),
+                h1_parser_config: &Default::default(),
                 h1_max_headers: None,
                 preserve_header_case: false,
                 #[cfg(feature = "ffi")]
diff --git a/src/proto/h1/mod.rs b/src/proto/h1/mod.rs
index a8f36f5fd9..1fea370cc5 100644
--- a/src/proto/h1/mod.rs
+++ b/src/proto/h1/mod.rs
@@ -71,7 +71,7 @@ pub(crate) struct ParsedMessage<T> {
 pub(crate) struct ParseContext<'a> {
     cached_headers: &'a mut Option<HeaderMap>,
     req_method: &'a mut Option<Method>,
-    h1_parser_config: ParserConfig,
+    h1_parser_config: &'a ParserConfig,
     h1_max_headers: Option<usize>,
     preserve_header_case: bool,
     #[cfg(feature = "ffi")]
diff --git a/src/proto/h1/role.rs b/src/proto/h1/role.rs
index f92092e5a9..92cbcccb88 100644
--- a/src/proto/h1/role.rs
+++ b/src/proto/h1/role.rs
@@ -1674,7 +1674,7 @@ mod tests {
             ParseContext {
                 cached_headers: &mut None,
                 req_method: &mut method,
-                h1_parser_config: Default::default(),
+                h1_parser_config: &Default::default(),
                 h1_max_headers: None,
                 preserve_header_case: false,
                 #[cfg(feature = "ffi")]
@@ -1702,7 +1702,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut Some(crate::Method::GET),
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1726,7 +1726,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut None,
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1747,7 +1747,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut Some(crate::Method::GET),
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1770,7 +1770,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut Some(crate::Method::GET),
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1797,7 +1797,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut Some(crate::Method::GET),
-            h1_parser_config,
+            h1_parser_config: &h1_parser_config,
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1821,7 +1821,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut Some(crate::Method::GET),
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1849,7 +1849,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut method,
-            h1_parser_config,
+            h1_parser_config: &h1_parser_config,
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1876,7 +1876,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut None,
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: false,
             #[cfg(feature = "ffi")]
@@ -1896,7 +1896,7 @@ mod tests {
         let ctx = ParseContext {
             cached_headers: &mut None,
             req_method: &mut None,
-            h1_parser_config: Default::default(),
+            h1_parser_config: &Default::default(),
             h1_max_headers: None,
             preserve_header_case: true,
             #[cfg(feature = "ffi")]
@@ -1935,7 +1935,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut None,
                     req_method: &mut None,
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -1956,7 +1956,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut None,
                     req_method: &mut None,
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -2186,7 +2186,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut None,
                     req_method: &mut Some(Method::GET),
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -2207,7 +2207,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut None,
                     req_method: &mut Some(m),
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -2228,7 +2228,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut None,
                     req_method: &mut Some(Method::GET),
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -2798,7 +2798,7 @@ mod tests {
             ParseContext {
                 cached_headers: &mut None,
                 req_method: &mut Some(Method::GET),
-                h1_parser_config: Default::default(),
+                h1_parser_config: &Default::default(),
                 h1_max_headers: None,
                 preserve_header_case: false,
                 #[cfg(feature = "ffi")]
@@ -2842,7 +2842,7 @@ mod tests {
                     ParseContext {
                         cached_headers: &mut None,
                         req_method: &mut None,
-                        h1_parser_config: Default::default(),
+                        h1_parser_config: &Default::default(),
                         h1_max_headers: max_headers,
                         preserve_header_case: false,
                         #[cfg(feature = "ffi")]
@@ -2866,7 +2866,7 @@ mod tests {
                     ParseContext {
                         cached_headers: &mut None,
                         req_method: &mut None,
-                        h1_parser_config: Default::default(),
+                        h1_parser_config: &Default::default(),
                         h1_max_headers: max_headers,
                         preserve_header_case: false,
                         #[cfg(feature = "ffi")]
@@ -3035,7 +3035,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut headers,
                     req_method: &mut None,
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
@@ -3080,7 +3080,7 @@ mod tests {
                 ParseContext {
                     cached_headers: &mut headers,
                     req_method: &mut None,
-                    h1_parser_config: Default::default(),
+                    h1_parser_config: &Default::default(),
                     h1_max_headers: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]