From 165ba64f685b1bce6dfe4c70758f1ba15ac160a4 Mon Sep 17 00:00:00 2001
From: Shaisolaris <66793913+Shaisolaris@users.noreply.github.com>
Date: Mon, 12 Oct 2026 02:26:31 -0700
Subject: [PATCH] Fix the default write buffer low-water mark

UVBaseTransport set its initial low-water mark to
FLOW_CONTROL_HIGH_WATER // 4, which is 16 bytes, while the high-water
mark is FLOW_CONTROL_HIGH_WATER * 1024. asyncio and
set_write_buffer_limits() both use high // 4, which is 16 KiB.
---
 tests/test_tcp.py                | 2 ++
 uvloop/handles/basetransport.pyx | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/test_tcp.py b/tests/test_tcp.py
index b933166b7..1f9392106 100644
--- a/tests/test_tcp.py
+++ b/tests/test_tcp.py
@@ -1349,6 +1349,8 @@ def resume_writing(self):
 
             t, p = await self.loop.create_connection(Protocol, *addr)
 
+            self.assertEqual(t.get_write_buffer_limits(), (16384, 65536))
+
             t.write(b'q' * 512)
             t.set_write_buffer_limits(low=16385)
             self.assertEqual(t.get_write_buffer_limits(), (16385, 65540))
diff --git a/uvloop/handles/basetransport.pyx b/uvloop/handles/basetransport.pyx
index 28b307947..246865760 100644
--- a/uvloop/handles/basetransport.pyx
+++ b/uvloop/handles/basetransport.pyx
@@ -3,7 +3,7 @@ cdef class UVBaseTransport(UVSocketHandle):
     def __cinit__(self):
         # Flow control
         self._high_water = FLOW_CONTROL_HIGH_WATER * 1024
-        self._low_water = FLOW_CONTROL_HIGH_WATER // 4
+        self._low_water = FLOW_CONTROL_HIGH_WATER * 1024 // 4
 
         self._protocol = None
         self._protocol_connected = 0