net: poll/select low latency socket support
select/poll busy-poll support.
Split sysctl value into two separate ones, one for read and one for poll.
updated Documentation/sysctl/net.txt
Add a new poll flag POLL_LL. When this flag is set, sock_poll will call
sk_poll_ll if possible. sock_poll sets this flag in its return value
to indicate to select/poll when a socket that can busy poll is found.
When poll/select have nothing to report, call the low-level
sock_poll again until we are out of time or we find something.
Once the system call finds something, it stops setting POLL_LL, so it can
return the result to the user ASAP.
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/socket.c b/net/socket.c
index 3eec3f7..4da14cb 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -107,6 +107,7 @@
#include <net/ll_poll.h>
#ifdef CONFIG_NET_LL_RX_POLL
+unsigned int sysctl_net_ll_read __read_mostly;
unsigned int sysctl_net_ll_poll __read_mostly;
#endif
@@ -1147,13 +1148,24 @@
/* No kernel lock held - perfect */
static unsigned int sock_poll(struct file *file, poll_table *wait)
{
+ unsigned int ll_flag = 0;
struct socket *sock;
/*
* We can't return errors to poll, so it's either yes or no.
*/
sock = file->private_data;
- return sock->ops->poll(file, sock, wait);
+
+ if (sk_valid_ll(sock->sk)) {
+ /* this socket can poll_ll so tell the system call */
+ ll_flag = POLL_LL;
+
+ /* once, only if requested by syscall */
+ if (wait && (wait->_key & POLL_LL))
+ sk_poll_ll(sock->sk, 1);
+ }
+
+ return ll_flag | sock->ops->poll(file, sock, wait);
}
static int sock_mmap(struct file *file, struct vm_area_struct *vma)