[PATCH net-next] net: add scheduling point in recvmmsg/sendmmsg

From: Eric Dumazet <edumazet@google.com>

Applications often have to reduce number of datagrams
they receive or send per system call to avoid starvation problems.

Really the kernel should take care of this by using cond_resched(),
so that applications can experiment bigger batch sizes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/socket.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index d730ef9dfbf0..91c2de6f5020 100644
--- a/net/socket.c
+++ b/net/socket.c

@@ -2041,6 +2041,7 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 		if (err)
 			break;
 		++datagrams;
+		cond_resched();
 	}
 
 	fput_light(sock->file, fput_needed);

@@ -2236,6 +2237,7 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
 		/* Out of band data, return right away */
 		if (msg_sys.msg_flags & MSG_OOB)
 			break;
+		cond_resched();
 	}
 
 out_put:

From: Eric Dumazet <redacted>
Date: Fri, 08 Jan 2016 08:37:20 -0800

From: Eric Dumazet <edumazet@google.com>

Applications often have to reduce number of datagrams
they receive or send per system call to avoid starvation problems.

Really the kernel should take care of this by using cond_resched(),
so that applications can experiment bigger batch sizes.

Signed-off-by: Eric Dumazet <edumazet@google.com>

Seems reasonable, applied, thanks Eric.