Prevent do_tcp_sendpages() from calling tcp_push() (at least) once per
page. Instead, arrange for tcp_push() to be called (at least) once per
data payload. This results in more MSS-sized packets and fewer packets
overall (5-10% reduction in my tests with typical OSD request sizes).
See commits 2f53384424 ("tcp: allow splice() to build full TSO
packets"), 35f9c09fe9 ("tcp: tcp_sendpages() should call tcp_push()
once") and ae62ca7b03 ("tcp: fix MSG_SENDPAGE_NOTLAST logic") for
details.
Here is an example of a packet size histogram for 128K OSD requests
(MSS = 1448, top 5):
Before:
SIZE COUNT
1448 777700
952 127915
1200 39238
1219 9806
21 5675
After:
SIZE COUNT
1448 897280
21 6201
1019 2797
643 2739
376 2479
We could do slightly better by explicitly corking the socket but it's
not clear it's worth it.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
433b0a1295