On Tue, Aug 29, 2000 at 08:53:23AM +0200, Patrick Schaaf wrote:
> > However, I'd be glad if you could tell me why my writes block that
> > long. I'm certainly under 128MB of socket buffers, so the limits
> > (on my 1GB machine) should not be reached.
> >
> > How certain are you?
100%.
- I instrumented tcp_mem_schedule() with net_ratelimited printk()s in
all pressure / failure cases, and nothing is printed.
- the machine was freshly booted, and received 1000 connections serving
48kB each. All write()s took about 50ms.
- the same machine and same test, under 2.2.17pre18, works fine, with
the writes taking about 0.5ms.
- next, I set /proc/sys/net/ipv4/tcp_wmem to '65536 65536 131072',
without a change in result.
- next, I added a ratelimited printk to wait_for_tcp_memory(),
the only place I see in the write path which goes to sleep.
And indeed, this one triggers regularly. Tried again with tcp_wmem
set as above, and it triggers just as often.
(just checked by reading SO_SNDBUF in my server, it is indeed shown
as 65536 byte)
What now?
best regards
Patrick
--- jake.2.4.0-test7-pre4-ippool/net/ipv4/tcp.c Fri Aug 18 08:22:48 2000
+++ jake.with.ank/net/ipv4/tcp.c Tue Aug 29 13:12:07 2000
@@ -460,20 +460,31 @@
/* Under limit. */
if (atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
- if (tcp_memory_pressure)
+ if (tcp_memory_pressure) {
tcp_memory_pressure = 0;
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: memory pressure is over, %d pages allocated\n",
+ atomic_read(&tcp_memory_allocated));
+ }
return 1;
}
/* Over hard limit. */
if (atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2]) {
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: under hard pressure, %d pages allocated\n",
+ atomic_read(&tcp_memory_allocated));
tcp_enter_memory_pressure();
goto suppress_allocation;
}
/* Under pressure. */
- if (atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[1])
+ if (atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[1]) {
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: coming under pressure, %d pages allocated\n",
+ atomic_read(&tcp_memory_allocated));
tcp_enter_memory_pressure();
+ }
if (kind) {
if (atomic_read(&sk->rmem_alloc) < sysctl_tcp_rmem[0])
@@ -492,6 +503,8 @@
suppress_allocation:
if (kind == 0) {
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: moderating sndbuf\n");
tcp_moderate_sndbuf(sk);
/* Fail only if socket is _under_ its sndbuf.
@@ -499,6 +512,8 @@
*/
if (sk->wmem_queued+size >= sk->sndbuf)
return 1;
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: moderated sndbuf, must fail\n");
}
/* Alas. Undo changes. */
@@ -853,6 +868,9 @@
current_timeo = vm_wait = (net_random()%(HZ/5))+2;
clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
+
+ if (net_ratelimit())
+ printk(KERN_INFO "TCP: waiting for memory\n");
add_wait_queue(sk->sleep, &wait);
for (;;) {
-
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