bpo-43317: Use io.DEFAULT_BUFFER_SIZE instead of 1024 in gzip CLI (#24645)

This improves the performance slightly.

Author: rhpvorderman

Lib/gzip.py

@@ -595,7 +595,7 @@ def main():
                 f = builtins.open(arg, "rb")
                 g = open(arg + ".gz", "wb")
         while True:
-            chunk = f.read(1024)
+            chunk = f.read(io.DEFAULT_BUFFER_SIZE)
             if not chunk:
                 break
             g.write(chunk)

Misc/NEWS.d/next/Library/2021-02-25-09-08-55.bpo-43317.qrOOpB.rst

@@ -0,0 +1,3 @@
+Set the chunk size for the ``gzip`` module main function to
+io.DEFAULT_BUFFER_SIZE. This is slightly faster than the 1024 bytes constant
+that was used previously.