Hello,

On Wed, 10 Dec 2003, David S. Miller wrote:

On Thu, 11 Dec 2003 02:06:09 +0200 (EET)
Julian Anastasov [off-list ref] wrote:

quoted

But the common average chain length for full table is 16 and the
different TOS values are usually 1 or 2 per path. We do not talk
about intentional DoS.

Your system has not configured it's rthash table size properly, see
recent discussions Robert has been making here.  You should have
rthash sized somewhere near the number of entries a full system
will have.

But regardless, let us say that your system has complexity O(16)
lookups as you mention, your proposal changes this to O(16+8).

	It is ~16 :)

	ip_rt_max_size = (rt_hash_mask + 1) * 16;

	This is what happens on full table, of course. OK,
some simple numbers for an ideal table:

- full table with 1024 chains, 16384 (max_size) entries equally
distributed in these 1024 chains, 16 per chain.

- there are 2048 paths with same saddr->daddr, each has 8 TOS values

2 cases depending on whether TOS is a hash key (path=saddr->daddr):

1. TOS is a hash key:

	- in each chain we have 16 paths, 1 TOS value per path
	- all 8 TOS values for a path are in 8 different chains

2. TOS is not a hash key:

	2 paths per chain (2 paths x 8 TOS values => 16 entries)

if all saddr->daddr->tos streams have same packet rate I think
the CPU time to lookup them will be same.
This is because 8 (number of TOS values) < 16 (chain length).

	And I hope the users always can tune the proposed TOS
settings if they see DoS and if they do not need TOS as a rt key.

Regards

--
Julian Anastasov [off-list ref]