On 08.11.2012 14:17, Andre Oppermann wrote:
On 07.11.2012 23:48, Alexander V. Chernikov wrote:
Hello list!
Currently size of arp/ndp hash is the following:
#define LLTBL_HASHTBL_SIZE 32 /* default 32 ? */
This may be OK for end hosts, but this is definitely not enough for
router howadays. Especially
given that IPv6 hosts generate 2 ndp records.
Output from 2 random v4 / v6 routers from my $job:
2:23 [0] m@matisse arp -an | wc -l
1494
2:24 [0] m@singapore ndp -an | wc -l
3999
Given that LIST_HEAD is just a pointer, and we currently have single
global (actually per-VNET)
instance for every l3 proto, bumping hash to, say, at least 4096
should do no harm.
A small list per hash bucket isn't bad. The hash should be about 1/4
of the expected table size.
One problem here may be the memory consumption on smaller systems. A
very large hash table size may hurt and isn't needed for a few entries.
I was afraid of proposing too small hash size. 4k costs 16kbytes which
is not much nowadays :)
For a compromise I'd say the default hash table size should be 256 or 512.
For me, 512 seems to be quite good default for generic box.
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