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>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 182364a..8f6056d 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -524,7 +524,7 @@ static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
                linear = len;
 
        skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
-                                  err);
+                                  err, 0);
        if (!skb)
                return NULL;
 

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index b163047..978d865 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -949,7 +949,7 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
                linear = len;
 
        skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
-                                  &err);
+                                  &err, 0);
        if (!skb)
                return ERR_PTR(err);
 

diff --git a/include/net/sock.h b/include/net/sock.h
index ab6a8b7..e4bbcbf 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1539,7 +1539,8 @@ extern struct sk_buff             *sock_alloc_send_pskb(struct sock *sk,
                                                      unsigned long header_len,
                                                      unsigned long data_len,
                                                      int noblock,
-                                                     int *errcode);
+                                                     int *errcode,
+                                                     int max_page_order);
 extern void *sock_kmalloc(struct sock *sk, int size,
                          gfp_t priority);
 extern void sock_kfree_s(struct sock *sk, void *mem, int size);

diff --git a/net/core/sock.c b/net/core/sock.c
index 83667de..5b6beba 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1741,24 +1741,23 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
 
 struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
                                     unsigned long data_len, int noblock,
-                                    int *errcode)
+                                    int *errcode, int max_page_order)
 {
-       struct sk_buff *skb;
+       struct sk_buff *skb = NULL;
+       unsigned long chunk;
        gfp_t gfp_mask;
        long timeo;
        int err;
        int npages = (data_len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
+       struct page *page;
+       int i;
 
        err = -EMSGSIZE;
        if (npages > MAX_SKB_FRAGS)
                goto failure;
 
-       gfp_mask = sk->sk_allocation;
-       if (gfp_mask & __GFP_WAIT)
-               gfp_mask |= __GFP_REPEAT;
-
        timeo = sock_sndtimeo(sk, noblock);
-       while (1) {
+       while (!skb) {
                err = sock_error(sk);
                if (err != 0)
                        goto failure;
@@ -1767,50 +1766,52 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
                if (sk->sk_shutdown & SEND_SHUTDOWN)
                        goto failure;
 
-               if (atomic_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf) {
-                       skb = alloc_skb(header_len, gfp_mask);
-                       if (skb) {
-                               int i;
-
-                               /* No pages, we're done... */
-                               if (!data_len)
-                                       break;
-
-                               skb->truesize += data_len;
-                               skb_shinfo(skb)->nr_frags = npages;
-                               for (i = 0; i < npages; i++) {
-                                       struct page *page;
-
-                                       page = alloc_pages(sk->sk_allocation, 0);
-                                       if (!page) {
-                                               err = -ENOBUFS;
-                                               skb_shinfo(skb)->nr_frags = i;
-                                               kfree_skb(skb);
-                                               goto failure;
-                                       }
-
-                                       __skb_fill_page_desc(skb, i,
-                                                       page, 0,
-                                                       (data_len >= PAGE_SIZE ?
-                                                        PAGE_SIZE :
-                                                        data_len));
-                                       data_len -= PAGE_SIZE;
-                               }
+               if (atomic_read(&sk->sk_wmem_alloc) >= sk->sk_sndbuf) {
+                       set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+                       set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+                       err = -EAGAIN;
+                       if (!timeo)
+                               goto failure;
+                       if (signal_pending(current))
+                               goto interrupted;
+                       timeo = sock_wait_for_wmem(sk, timeo);
+                       continue;
+               }
 
-                               /* Full success... */
-                               break;
-                       }
-                       err = -ENOBUFS;
+               err = -ENOBUFS;
+               gfp_mask = sk->sk_allocation;
+               if (gfp_mask & __GFP_WAIT)
+                       gfp_mask |= __GFP_REPEAT;
+
+               skb = alloc_skb(header_len, gfp_mask);
+               if (!skb)
                        goto failure;
+
+               skb->truesize += data_len;
+
+               for (i = 0; npages > 0; i++) {
+                       int order = max_page_order;
+
+                       while (order) {
+                               if (npages >= 1 << order) {
+                                       page = alloc_pages(sk->sk_allocation |
+                                                          __GFP_COMP | __GFP_NOWARN,
+                                                          order);
+                                       if (page)
+                                               goto fill_page;
+                               }
+                               order--;
+                       }
+                       page = alloc_page(sk->sk_allocation);
+                       if (!page)
+                               goto failure;
+fill_page:
+                       chunk = min_t(unsigned long, data_len,
+                                     PAGE_SIZE << order);
+                       skb_fill_page_desc(skb, i, page, 0, chunk);
+                       data_len -= chunk;
+                       npages -= 1 << order;
                }
-               set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
-               set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
-               err = -EAGAIN;
-               if (!timeo)
-                       goto failure;
-               if (signal_pending(current))
-                       goto interrupted;
-               timeo = sock_wait_for_wmem(sk, timeo);
        }
 
        skb_set_owner_w(skb, sk);
@@ -1819,6 +1820,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
 interrupted:
        err = sock_intr_errno(timeo);
 failure:
+       kfree_skb(skb);
        *errcode = err;
        return NULL;
 }
@@ -1827,7 +1829,7 @@ EXPORT_SYMBOL(sock_alloc_send_pskb);
 struct sk_buff *sock_alloc_send_skb(struct sock *sk, unsigned long size,
                                    int noblock, int *errcode)
 {
-       return sock_alloc_send_pskb(sk, size, 0, noblock, errcode);
+       return sock_alloc_send_pskb(sk, size, 0, noblock, errcode, 0);
 }
 EXPORT_SYMBOL(sock_alloc_send_skb);
 

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 4cb28a7..6c53dd9 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2181,7 +2181,7 @@ static struct sk_buff *packet_alloc_skb(struct sock *sk, size_t prepad,
                linear = len;
 
        skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
-                                  err);
+                                  err, 0);
        if (!skb)
                return NULL;
 

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 99dc760..fee9e33 100644 (file)
--- 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;