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SubjectRe: Out of socket memory? (2.4.0-test11)
Dan Kegel wrote:
> Daniel Walton ( wrote:
> > I've been having a problem with a high volume Linux web server. This
> > particular web server used to be a FreeBSD machine and I've been trying to
> > successfully make the switch for some time now. I've been trying the 2.4
> > development kernels as they come out and I've been tweaking the /proc
> > filesystem variables but so far nothing seems to have fixed the
> > problem. The problem is that I get "Out of socket memory" errors and the
> > networking locks up...
> FWIW, the code that prints this is in ipv4/tcp_timer.c
> and it looks like it's a DoS attack countermeasure.
> /* Do not allow orphaned sockets to eat all our resources.
> * This is direct violation of TCP specs, but it is required
> * to prevent DoS attacks. It is called when a retransmission timeout
> * or zero probe timeout occurs on orphaned socket.
> ...
> if (orphans >= sysctl_tcp_max_orphans ||
> (sk->wmem_queued > SOCK_MIN_SNDBUF &&
> atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2])) {
> if (net_ratelimit())
> printk(KERN_INFO "Out of socket memory\n");

See Documentation/networking/ip-sysctl.txt for more info and tuning
suggestions, esp. tcp_orphan_retries and tcp_max_orphans.
An orphaned socket is one that has at least partially
opened, but has not been fully accepted. You might try reducing

It looks like you can view the current number of orphans at
/proc/net/sockstat or something like that.

* Report socket allocation statistics []
int afinet_get_info(char *buffer, char **start, off_t offset, int length)
/* From net/socket.c */
extern int socket_get_info(char *, char **, off_t, int);

int len = socket_get_info(buffer,start,offset,length);

len += sprintf(buffer+len,"TCP: inuse %d orphan %d tw %d alloc %d mem %d\n",
atomic_read(&tcp_orphan_count), tcp_tw_count,

- Dan
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