net: attempt high order allocations in sock_alloc_send_pskb()

Adding paged frags skbs to af_unix sockets introduced a performance
regression on large sends because of additional page allocations, even
if each skb could carry at least 100% more payload than before.

We can instruct sock_alloc_send_pskb() to attempt high order
allocations.

Most of the time, it does a single page allocation instead of 8.

I added an additional parameter to sock_alloc_send_pskb() to
let other users to opt-in for this new feature on followup patches.

Tested:

Before patch :

$ netperf -t STREAM_STREAM
STREAM STREAM TEST
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 2304  212992  212992    10.00    46861.15

After patch :

$ netperf -t STREAM_STREAM
STREAM STREAM TEST
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 2304  212992  212992    10.00    57981.11

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 99dc760cdd95..fee9e3397cd1 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1479,7 +1479,8 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
                                  MAX_SKB_FRAGS * PAGE_SIZE);
 
         skb = sock_alloc_send_pskb(sk, len - data_len, data_len,
-                                   msg->msg_flags & MSG_DONTWAIT, &err);
+                                   msg->msg_flags & MSG_DONTWAIT, &err,
+                                   PAGE_ALLOC_COSTLY_ORDER);
         if (skb == NULL)
                 goto out;
 
@@ -1651,7 +1652,8 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 data_len = max_t(int, 0, size - SKB_MAX_HEAD(0));
 
                 skb = sock_alloc_send_pskb(sk, size - data_len, data_len,
-                                           msg->msg_flags & MSG_DONTWAIT, &err);
+                                           msg->msg_flags & MSG_DONTWAIT, &err,
+                                           get_order(UNIX_SKB_FRAGS_SZ));
                 if (!skb)
                         goto out_err;