[dpdk-dev] Defaults for rte_hash

[Matthew Hall <mhall@mhcomputing.net>]

Hello,

I was looking at the code which inits rte_hash objects in examples/l3fwd. It's 
using approx. 1M to 4M hash 'entries' depending on 32-bit vs 64-bit, but it's 
setting the 'bucket_entries' to just 4.

Normally I'm used to using somewhat deeper hash buckets than that... it seems 
like having a zillion little tiny hash buckets would cause more TLB pressure 
and memory overhead... or does 4 get shifted / exponentiated into 2**4 ?

The documentation in http://dpdk.org/doc/api/structrte__hash__parameters.html 
and http://dpdk.org/doc/api/rte__hash_8h.html isn't that clear... is there a 
better place to look for this?

In my case I'm looking to create a table of 4M or 8M entries, containing 
tables of security threat IPs / domains, to be detected in the traffic. So it 
would be good to have some understanding how not to waste a ton of memory on a 
table this huge without making it run super slow either.

Did anybody have some experience with how to get this right?

Another thing... the LPM table uses 16-bit Hop IDs. But I would probably have 
more than 64K CIDR blocks of badness on the Internet available to me for 
analysis. How would I cope with this, besides just letting some attackers 
escape unnoticed? ;)

Have we got some kind of structure which allows a greater number of CIDRs even 
if it's not quite as fast?

Thanks,
Matthew.