We're spending a considerable amount of the sendmsg/recvmsg time just
copying in the message header. And for provided buffers, the known
single entry iovec.
Be a bit smarter about it and enable/disable user access around our
copying. In a test case that does both sendmsg and recvmsg, the
runtime before this change (averaged over multiple runs, very stable
times however):
Kernel Time Diff
====================================
-git 4720 usec
-git+commit 4311 usec -8.7%
and looking at a profile diff, we see the following:
0.25% +9.33% [kernel.kallsyms] [k] _copy_from_user
4.47% -3.32% [kernel.kallsyms] [k] __io_msg_copy_hdr.constprop.0
where we drop more than 9% of _copy_from_user() time, and consequently
add time to __io_msg_copy_hdr() where the copies are now attributed to,
but with a net win of 6%.
In comparison, the same test case with send/recv runs in 3745 usec, which
is (expectedly) still quite a bit faster. But at least sendmsg/recvmsg is
now only ~13% slower, where it was ~21% slower before.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
io_uring/net.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/io_uring/net.c b/io_uring/net.c
index 7a07c5563d66..83fba2882720 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -255,27 +255,42 @@ static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
int ret;
- if (copy_from_user(msg, sr->umsg, sizeof(*sr->umsg)))
+ if (!user_access_begin(sr->umsg, sizeof(*sr->umsg)))
return -EFAULT;
+ ret = -EFAULT;
+ unsafe_get_user(msg->msg_name, &sr->umsg->msg_name, ua_end);
+ unsafe_get_user(msg->msg_namelen, &sr->umsg->msg_namelen, ua_end);
+ unsafe_get_user(msg->msg_iov, &sr->umsg->msg_iov, ua_end);
+ unsafe_get_user(msg->msg_iovlen, &sr->umsg->msg_iovlen, ua_end);
+ unsafe_get_user(msg->msg_control, &sr->umsg->msg_control, ua_end);
+ unsafe_get_user(msg->msg_controllen, &sr->umsg->msg_controllen, ua_end);
+ msg->msg_flags = 0;
+
if (req->flags & REQ_F_BUFFER_SELECT) {
if (msg->msg_iovlen == 0) {
sr->len = iomsg->fast_iov[0].iov_len = 0;
iomsg->fast_iov[0].iov_base = NULL;
iomsg->free_iov = NULL;
} else if (msg->msg_iovlen > 1) {
- return -EINVAL;
+ ret = -EINVAL;
+ goto ua_end;
} else {
- if (copy_from_user(iomsg->fast_iov, msg->msg_iov,
- sizeof(*msg->msg_iov)))
- return -EFAULT;
+ /* we only need the length for provided buffers */
+ if (!access_ok(&msg->msg_iov[0].iov_len, sizeof(__kernel_size_t)))
+ goto ua_end;
+ unsafe_get_user(iomsg->fast_iov[0].iov_len,
+ &msg->msg_iov[0].iov_len, ua_end);
sr->len = iomsg->fast_iov[0].iov_len;
iomsg->free_iov = NULL;
}
-
- return 0;
+ ret = 0;
+ua_end:
+ user_access_end();
+ return ret;
}
+ user_access_end();
iomsg->free_iov = iomsg->fast_iov;
ret = __import_iovec(ddir, msg->msg_iov, msg->msg_iovlen, UIO_FASTIOV,
&iomsg->free_iov, &iomsg->msg.msg_iter, false);
--
2.43.0
