| Message ID | 1300662282-24741-2-git-send-email-hagen@jauu.net |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
Le lundi 21 mars 2011 à 00:04 +0100, Hagen Paul Pfeifer a écrit : > In the case that a server programmer misjudge network characteristic the > backlog parameter for listen(2) may not adequate to utilize hosts > capabilities and lead to unrequired SYN retransmission - a small backlog > value can form an artificial limitation. From Erics server setup, a > listen queue length of 8 is often a way to small): > > ss -a | head > State Recv-Q Send-Q Local Address:Port Peer > Address:Port > LISTEN 0 8 *:imaps *:* > LISTEN 0 8 *:pop3s *:* > LISTEN 0 50 *:mysql *:* > LISTEN 0 8 *:pop3 *:* > LISTEN 0 8 *:imap2 *:* > LISTEN 0 511 *:www *:* > > Until now it is not possible for the system (network) administrator to > increase this value. A bug report must be filled, the backlog increased, > a new version released or even worse: if using closed source software > you cannot make anything. > > sysctl_min_syn_backlog provides the ability to increase the minimum > queue length. The default is 8. > > Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net> > > --- > I will spin a second documentation patch if Davem accept this patch. > --- > include/net/request_sock.h | 1 + > net/core/request_sock.c | 5 ++++- > net/ipv4/sysctl_net_ipv4.c | 7 +++++++ > 3 files changed, 12 insertions(+), 1 deletions(-) > > diff --git a/include/net/request_sock.h b/include/net/request_sock.h > index 99e6e19..3e8865f 100644 > --- a/include/net/request_sock.h > +++ b/include/net/request_sock.h > @@ -89,6 +89,7 @@ static inline void reqsk_free(struct request_sock *req) > } > > extern int sysctl_max_syn_backlog; > +extern int sysctl_min_syn_backlog; > > /** struct listen_sock - listen state > * > diff --git a/net/core/request_sock.c b/net/core/request_sock.c > index 182236b..e937e9c 100644 > --- a/net/core/request_sock.c > +++ b/net/core/request_sock.c > @@ -35,6 +35,9 @@ > int sysctl_max_syn_backlog = 256; > EXPORT_SYMBOL(sysctl_max_syn_backlog); > > +int sysctl_min_syn_backlog = 8; > +EXPORT_SYMBOL(sysctl_min_syn_backlog); > + > int reqsk_queue_alloc(struct request_sock_queue *queue, > unsigned int nr_table_entries) > { > @@ -42,7 +45,7 @@ int reqsk_queue_alloc(struct request_sock_queue *queue, > 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 = max_t(u32, nr_table_entries, sysctl_min_syn_backlog); > 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) I believe you are mistaken. The code you change is the code sizing the hash table, not sk->sk_max_ack_backlog This only matters if one application is able to change its listen backlog during its lifetime. Say, it begins with : listen(fd, 1); Then, a bit later : listen(fd, 8192); This certainly is very unlikely... With current kernel, it does change the maximum SYN_RECV sockets in flight, but hash table is not resized and stay with 8 slots, so performance might be suboptimal, since chains are going to hold 1024 elements. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/net/request_sock.h b/include/net/request_sock.h index 99e6e19..3e8865f 100644 --- a/include/net/request_sock.h +++ b/include/net/request_sock.h @@ -89,6 +89,7 @@ static inline void reqsk_free(struct request_sock *req) } extern int sysctl_max_syn_backlog; +extern int sysctl_min_syn_backlog; /** struct listen_sock - listen state * diff --git a/net/core/request_sock.c b/net/core/request_sock.c index 182236b..e937e9c 100644 --- a/net/core/request_sock.c +++ b/net/core/request_sock.c @@ -35,6 +35,9 @@ int sysctl_max_syn_backlog = 256; EXPORT_SYMBOL(sysctl_max_syn_backlog); +int sysctl_min_syn_backlog = 8; +EXPORT_SYMBOL(sysctl_min_syn_backlog); + int reqsk_queue_alloc(struct request_sock_queue *queue, unsigned int nr_table_entries) { @@ -42,7 +45,7 @@ int reqsk_queue_alloc(struct request_sock_queue *queue, 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 = max_t(u32, nr_table_entries, sysctl_min_syn_backlog); 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) diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 1a45665..cc03c62 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -298,6 +298,13 @@ static struct ctl_table ipv4_table[] = { .proc_handler = proc_dointvec }, { + .procname = "tcp_min_syn_backlog", + .data = &sysctl_min_syn_backlog, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, + { .procname = "ip_local_port_range", .data = &sysctl_local_ports.range, .maxlen = sizeof(sysctl_local_ports.range),
In the case that a server programmer misjudge network characteristic the backlog parameter for listen(2) may not adequate to utilize hosts capabilities and lead to unrequired SYN retransmission - a small backlog value can form an artificial limitation. From Erics server setup, a listen queue length of 8 is often a way to small): ss -a | head State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 8 *:imaps *:* LISTEN 0 8 *:pop3s *:* LISTEN 0 50 *:mysql *:* LISTEN 0 8 *:pop3 *:* LISTEN 0 8 *:imap2 *:* LISTEN 0 511 *:www *:* Until now it is not possible for the system (network) administrator to increase this value. A bug report must be filled, the backlog increased, a new version released or even worse: if using closed source software you cannot make anything. sysctl_min_syn_backlog provides the ability to increase the minimum queue length. The default is 8. Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net> --- I will spin a second documentation patch if Davem accept this patch. --- include/net/request_sock.h | 1 + net/core/request_sock.c | 5 ++++- net/ipv4/sysctl_net_ipv4.c | 7 +++++++ 3 files changed, 12 insertions(+), 1 deletions(-)