Sorry for polluting the list, not sure why the cover-letter isn't
wired with the other patches..
Regards,
Hao
On 5/8/22 23:37, Hao Xu wrote:
From: Hao Xu <howeyxu@xxxxxxxxxxx>
Let multishot support multishot mode, currently only add accept as its
first consumer.
theoretical analysis:
1) when connections come in fast
- singleshot:
add accept sqe(userspace) --> accept inline
^ |
|-----------------|
- multishot:
add accept sqe(userspace) --> accept inline
^ |
|--*--|
we do accept repeatedly in * place until get EAGAIN
2) when connections come in at a low pressure
similar thing like 1), we reduce a lot of userspace-kernel context
switch and useless vfs_poll()
tests:
Did some tests, which goes in this way:
server client(multiple)
accept connect
read write
write read
close close
Basically, raise up a number of clients(on same machine with server) to
connect to the server, and then write some data to it, the server will
write those data back to the client after it receives them, and then
close the connection after write return. Then the client will read the
data and then close the connection. Here I test 10000 clients connect
one server, data size 128 bytes. And each client has a go routine for
it, so they come to the server in short time.
test 20 times before/after this patchset, time spent:(unit cycle, which
is the return value of clock())
before:
1930136+1940725+1907981+1947601+1923812+1928226+1911087+1905897+1941075
+1934374+1906614+1912504+1949110+1908790+1909951+1941672+1969525+1934984
+1934226+1914385)/20.0 = 1927633.75
after:
1858905+1917104+1895455+1963963+1892706+1889208+1874175+1904753+1874112
+1874985+1882706+1884642+1864694+1906508+1916150+1924250+1869060+1889506
+1871324+1940803)/20.0 = 1894750.45
(1927633.75 - 1894750.45) / 1927633.75 = 1.65%
v1->v2:
- re-implement it against the reworked poll code
v2->v3:
- fold in code tweak and clean from Jens
- use io_issue_sqe rather than io_queue_sqe, since the former one
return the internal error back which makes more sense
- remove io_poll_clean() and its friends since they are not needed
v3->v4:
- move the accept multishot flag to the proper patch
- typo correction
- remove improperly added signed-off-by
v4->v5:
- address some email account issue..
Hao Xu (4):
io_uring: add IORING_ACCEPT_MULTISHOT for accept
io_uring: add REQ_F_APOLL_MULTISHOT for requests
io_uring: let fast poll support multishot
io_uring: implement multishot mode for accept
fs/io_uring.c | 94 +++++++++++++++++++++++++++--------
include/uapi/linux/io_uring.h | 5 ++
2 files changed, 79 insertions(+), 20 deletions(-)
base-commit: 0a194603ba7ee67b4e39ec0ee5cda70a356ea618
