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Re: FIB alternative fib_hash2.c

To: Robert Olsson <Robert.Olsson@xxxxxxxxxxx>
Subject: Re: FIB alternative fib_hash2.c
From: Andre Tomt <andre@xxxxxxxx>
Date: Sat, 16 Apr 2005 10:55:07 +0200
Cc: netdev@xxxxxxxxxxx
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Robert Olsson wrote:
Andre Tomt writes:

> Drool. Got some numbers? pps - flows - memory use, on what hardware, > that sort of thing.

For testing reasons I use pure rDoS with 1 dst per packet. Routing table is taken from bgp route some year ago w 123 kroutes.

 Also to test just FIB lookup I use the preroute paches to bypass dst
 hash this only works with gatewayed routes  which is fine for me.

 Some numbers from a 1.6 GHz Opteron. rDoS at 720 kpps injected in eth0.
 result is what get out on eth1, eth3.


Current FIB -----------
Iface   MTU Met  RX-OK RX-ERR RX-DRP RX-OVR  TX-OK TX-ERR TX-DRP TX-OVR Flags
eth0   1500   0 2346827 9125541 9125541 7653595    262      0      0      0 BRU
eth1   1500   0      4      0      0      0 2325770      0      0      0 BRU
eth2   1500   0      0      0      0      0      5      0      0      0 BRU
eth3   1500   0      1      0      0      0  20652      0      0      0 BRU
eth4   1500   0      0      0      0      0      5      0      0      0 BRU


New hash2
----------
eth0   1500   0 4389455 8372826 8372826 5610843    199      0      0      0 BRU
eth1   1500   0      2      0      0      0 4349633      0      0      0 BRU
eth2   1500   0      0      0      0      0      5      0      0      0 BRU
eth3   1500   0      1      0      0      0  38875      0      0      0 BRU
eth4   1500   0      0      0      0      0      5      0      0      0 BRU


168 kpps vs 316 kpps on this box so quite substantial improvement and if you can merge local and main table you get even more. Well to honest we can merge tables do this current FIB too.

Nice. What kind of equipment and/or software do you use to generate this sort of traffic pattern? And how much is one expected to gain by merging local and main tables? I try to avoid policy routing wherever possible - so merging is very interesting indeed.

Mem usage
IP: FIB vers 0.58 routing table of 16777216 buckets, 65536Kbytes for table 
id=255

So ~66 MB for hash structure to that comes routing info this can too a lot
as hash2 makes  /24 prefix-clones of prefixes in range 0>plen>24, I see
294 MB for the full BGP table.

I reckon this would be limited to available lowmem on 32bit (ick) systems?

I have some single flow numbers if you are interested too.

If its not too much trouble I would apriciate it.

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