Re: Is kernel 2.6.11 adjust tcp_max_syn_backlog incorrectly?

Skywind [off-list ref] writes:

It seems that kernel don't adjust these value automatic, is this a bug?

I guess the mechanism of tcp.c in 2.6.11 have some changes(between
2.6.10), and it conduce to this result,
Is this guess correctly?

Yes, there were some changes here when it was converted to a common
function for all hash tables (alloc_large_system_hash - the function
with the argument list from hell).  Anyways, here's a quick fix.

DaveM for your consideration.

Adjust TCP mem order check to new alloc_large_system_hash

Signed-off-by: Andi Kleen <redacted>

--- linux-2.6.11-work/net/ipv4/tcp.c~	2005-03-02 08:37:51.000000000 +0100
+++ linux-2.6.11-work/net/ipv4/tcp.c	2005-06-11 12:16:22.000000000 +0200

@@ -2337,7 +2337,7 @@
 			(tcp_bhash_size * sizeof(struct tcp_bind_hashbucket));
 			order++)
 		;
-	if (order > 4) {
+	if (order >= 4) {
 		sysctl_local_port_range[0] = 32768;
 		sysctl_local_port_range[1] = 61000;
 		sysctl_tcp_max_tw_buckets = 180000;

From: Andi Kleen <redacted>
Date: Sat, 11 Jun 2005 12:25:08 +0200

Yes, there were some changes here when it was converted to a common
function for all hash tables (alloc_large_system_hash - the function
with the argument list from hell).  Anyways, here's a quick fix.

DaveM for your consideration.

Adjust TCP mem order check to new alloc_large_system_hash

Signed-off-by: Andi Kleen <redacted>

I just reread those NUMA changes, and they changed the heuristics
for sizing things at the same time as moving over to the
alloc_large_system_hash() change.

The change was to move from (21 - PAGE_SHIFT) and (23 - PAGE_SHIFT)
to (25 - PAGE_SHIFT) and (27 - PAGE_SHIFT) respectively.

This is the part of the NUMA TCP changes that made the sysctl setting
behavior differ.

Andi's patch is the least intrusive fix for 2.6.12, so I will
apply it.  But longer term these heuristics need to be revisited
as a whole.