commit 420092e255389008b399efa61db300fe44356ee8
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Mon May 28 18:42:45 2018 -0700
committer Ned Deily <nad@python.org> Mon May 28 21:42:45 2018 -0400
tree dac590abb3c2b8ce1eb396c51b9e5f1ada5e8982
parent a379dea11e989da73c335a83ea7368c5e070987e

bpo-32410: Avoid blocking on file IO in sendfile fallback code (GH-7172) (#7182)

(cherry picked from commit 7165754b6b5f3b7c07050d921fa1c58bba5f0ff1)

Co-authored-by: Yury Selivanov <yury@magic.io>

Lib/asyncio/base_events.py

diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index a0243f5..ffd2513 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -800,7 +800,10 @@
     async def _sock_sendfile_fallback(self, sock, file, offset, count):
         if offset:
             file.seek(offset)
-        blocksize = min(count, 16384) if count else 16384
+        blocksize = (
+            min(count, constants.SENDFILE_FALLBACK_READBUFFER_SIZE)
+            if count else constants.SENDFILE_FALLBACK_READBUFFER_SIZE
+        )
         buf = bytearray(blocksize)
         total_sent = 0
         try:
@@ -810,7 +813,7 @@
                     if blocksize <= 0:
                         break
                 view = memoryview(buf)[:blocksize]
-                read = file.readinto(view)
+                read = await self.run_in_executor(None, file.readinto, view)
                 if not read:
                     break  # EOF
                 await self.sock_sendall(sock, view)