[AF_UNIX]: use shift instead of integer division
The patch below replaces a divide by 2 with a shift -- sk_sndbuf is an
integer, so gcc emits an idiv, which takes 10x longer than a shift by 1.
This improves af_unix bandwidth by ~6-10K/s. Also, tidy up the comment
to fit in 80 columns while we're at it.
Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index c323cc6..2b00460 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1427,15 +1427,15 @@
while(sent < len)
{
/*
- * Optimisation for the fact that under 0.01% of X messages typically
- * need breaking up.
+ * Optimisation for the fact that under 0.01% of X
+ * messages typically need breaking up.
*/
- size=len-sent;
+ size = len-sent;
/* Keep two messages in the pipe so it schedules better */
- if (size > sk->sk_sndbuf / 2 - 64)
- size = sk->sk_sndbuf / 2 - 64;
+ if (size > ((sk->sk_sndbuf >> 1) - 64))
+ size = (sk->sk_sndbuf >> 1) - 64;
if (size > SKB_MAX_ALLOC)
size = SKB_MAX_ALLOC;