[NET]: Size listen hash tables using backlog hint

We currently allocate a fixed size (TCP_SYNQ_HSIZE=512) slots hash table for
each LISTEN socket, regardless of various parameters (listen backlog for
example)

On x86_64, this means order-1 allocations (might fail), even for 'small'
sockets, expecting few connections. On the contrary, a huge server wanting a
backlog of 50000 is slowed down a bit because of this fixed limit.

This patch makes the sizing of listen hash table a dynamic parameter,
depending of :
- net.core.somaxconn tunable (default is 128)
- net.ipv4.tcp_max_syn_backlog tunable (default : 256, 1024 or 128)
- backlog value given by user application  (2nd parameter of listen())

For large allocations (bigger than PAGE_SIZE), we use vmalloc() instead of
kmalloc().

We still limit memory allocation with the two existing tunables (somaxconn &
tcp_max_syn_backlog). So for standard setups, this patch actually reduce RAM
usage.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 35 insertions, 20 deletions

diff --git a/net/core/request_sock.c b/net/core/request_sock.c
index 79ebd75fbe4d..5f0818d815e6 100644
--- a/net/core/request_sock.c
+++ b/net/core/request_sock.c
@@ -15,6 +15,7 @@
 #include <linux/random.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/vmalloc.h>
 
 #include <net/request_sock.h>
 
@@ -29,22 +30,31 @@
  * it is absolutely not enough even at 100conn/sec. 256 cures most
  * of problems. This value is adjusted to 128 for very small machines
  * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).
- * Further increasing requires to change hash table size.
+ * Note : Dont forget somaxconn that may limit backlog too.
  */
 int sysctl_max_syn_backlog = 256;
 
 int reqsk_queue_alloc(struct request_sock_queue *queue,
-                      const int nr_table_entries)
+                      unsigned int nr_table_entries)
 {
-        const int lopt_size = sizeof(struct listen_sock) +
-                              nr_table_entries * sizeof(struct request_sock *);
-        struct listen_sock *lopt = kzalloc(lopt_size, GFP_KERNEL);
-
+        size_t lopt_size = sizeof(struct listen_sock);
+        struct listen_sock *lopt;
+
+        nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);
+        nr_table_entries = max_t(u32, nr_table_entries, 8);
+        nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
+        lopt_size += nr_table_entries * sizeof(struct request_sock *);
+        if (lopt_size > PAGE_SIZE)
+                lopt = __vmalloc(lopt_size,
+                        GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+                        PAGE_KERNEL);
+        else
+                lopt = kzalloc(lopt_size, GFP_KERNEL);
         if (lopt == NULL)
                 return -ENOMEM;
 
-        for (lopt->max_qlen_log = 6;
-             (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog;
+        for (lopt->max_qlen_log = 3;
+             (1 << lopt->max_qlen_log) < nr_table_entries;
              lopt->max_qlen_log++);
 
         get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
@@ -65,9 +75,11 @@ void reqsk_queue_destroy(struct request_sock_queue *queue)
 {
         /* make all the listen_opt local to us */
         struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
+        size_t lopt_size = sizeof(struct listen_sock) +
+                lopt->nr_table_entries * sizeof(struct request_sock *);
 
         if (lopt->qlen != 0) {
-                int i;
+                unsigned int i;
 
                 for (i = 0; i < lopt->nr_table_entries; i++) {
                         struct request_sock *req;
@@ -81,7 +93,10 @@ void reqsk_queue_destroy(struct request_sock_queue *queue)
         }
 
         BUG_TRAP(lopt->qlen == 0);
-        kfree(lopt);
+        if (lopt_size > PAGE_SIZE)
+                vfree(lopt);
+        else
+                kfree(lopt);
 }
 
 EXPORT_SYMBOL(reqsk_queue_destroy);
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index e08e7688a263..0a5d68dbb418 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -1022,7 +1022,7 @@ static void dccp_v4_reqsk_destructor(struct request_sock *req)
         kfree(inet_rsk(req)->opt);
 }
 
-static struct request_sock_ops dccp_request_sock_ops = {
+static struct request_sock_ops dccp_request_sock_ops _read_mostly = {
         .family         = PF_INET,
         .obj_size       = sizeof(struct dccp_request_sock),
         .rtx_syn_ack    = dccp_v4_send_response,
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 72cbdcfc2c65..047d170a363a 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -262,12 +262,12 @@ int dccp_destroy_sock(struct sock *sk)
 
 EXPORT_SYMBOL_GPL(dccp_destroy_sock);
 
-static inline int dccp_listen_start(struct sock *sk)
+static inline int dccp_listen_start(struct sock *sk, int backlog)
 {
         struct dccp_sock *dp = dccp_sk(sk);
 
         dp->dccps_role = DCCP_ROLE_LISTEN;
-        return inet_csk_listen_start(sk, TCP_SYNQ_HSIZE);
+        return inet_csk_listen_start(sk, backlog);
 }
 
 int dccp_disconnect(struct sock *sk, int flags)
@@ -788,7 +788,7 @@ int inet_dccp_listen(struct socket *sock, int backlog)
                  * FIXME: here it probably should be sk->sk_prot->listen_start
                  * see tcp_listen_start
                  */
-                err = dccp_listen_start(sk);
+                err = dccp_listen_start(sk, backlog);
                 if (err)
                         goto out;
         }
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index edcf0932ac6d..4a81d54a7569 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -204,7 +204,7 @@ int inet_listen(struct socket *sock, int backlog)
          * we can only allow the backlog to be adjusted.
          */
         if (old_state != TCP_LISTEN) {
-                err = inet_csk_listen_start(sk, TCP_SYNQ_HSIZE);
+                err = inet_csk_listen_start(sk, backlog);
                 if (err)
                         goto out;
         }
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 96bbe2a0aa1b..9d68837888d3 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -343,7 +343,7 @@ struct dst_entry* inet_csk_route_req(struct sock *sk,
 EXPORT_SYMBOL_GPL(inet_csk_route_req);
 
 static inline u32 inet_synq_hash(const __be32 raddr, const __be16 rport,
-                                 const u32 rnd, const u16 synq_hsize)
+                                 const u32 rnd, const u32 synq_hsize)
 {
         return jhash_2words((__force u32)raddr, (__force u32)rport, rnd) & (synq_hsize - 1);
 }
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 22ef8bd26620..5fbf96552cac 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -715,7 +715,7 @@ static struct ip_options *tcp_v4_save_options(struct sock *sk,
         return dopt;
 }
 
-struct request_sock_ops tcp_request_sock_ops = {
+struct request_sock_ops tcp_request_sock_ops __read_mostly = {
         .family         =       PF_INET,
         .obj_size       =       sizeof(struct tcp_request_sock),
         .rtx_syn_ack    =       tcp_v4_send_synack,
@@ -1385,7 +1385,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
         if (st->state == TCP_SEQ_STATE_OPENREQ) {
                 struct request_sock *req = cur;
 
-                icsk = inet_csk(st->syn_wait_sk);
+                icsk = inet_csk(st->syn_wait_sk);
                 req = req->dl_next;
                 while (1) {
                         while (req) {
@@ -1395,7 +1395,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
                                 }
                                 req = req->dl_next;
                         }
-                        if (++st->sbucket >= TCP_SYNQ_HSIZE)
+                        if (++st->sbucket >= icsk->icsk_accept_queue.listen_opt->nr_table_entries)
                                 break;
 get_req:
                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index eb6d145ecfd7..1a3c46c139f8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -526,7 +526,7 @@ static void tcp_v6_reqsk_destructor(struct request_sock *req)
                 kfree_skb(inet6_rsk(req)->pktopts);
 }
 
-static struct request_sock_ops tcp6_request_sock_ops = {
+static struct request_sock_ops tcp6_request_sock_ops _read_mostly = {
         .family         =       AF_INET6,
         .obj_size       =       sizeof(struct tcp6_request_sock),
         .rtx_syn_ack    =       tcp_v6_send_synack,