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Greetings Wayne,
: I am trying to determine how to best increase the number of
: routing tables available in linux 2.6 to more than 255.
You are in good company. The question seems to come up with some
frequency [0]...I'm beginning to think that it needs to be an FAQ.
: I realize this involves increasing the storage of some messages
: to and from the kernel in addition to kernel changes (from
: browsing the code), and was hopeful that someone might know what
: the correct solution would be or could point me in the right
: direction (like existing patches or a highlevel of what I need to
: change in the code).
Sadly, I haven't heard of anybody yet having done this, although one
of the key developers of the kernel VLAN code (Ben Greear) has
recently requested development on this point [1].
: Additionally, I was curious how the ip *rule* system works in
: regards to matching -- is it a linear search or optimized in some
: way. Basically what I'm asking is if adding rules to a machine
: adds time to the whole system passing over various rules that
: don't match.
While I'm not certain of this, I believe that any route lookup which
fails the routing cache (you do know about the routing cache, right)
will traverse the rule policy database in a linear fashion. (Sorry,
don't know which part of the kernel C to examine.)
: This all comes down to a seutp I have that has a lot of routing
: tables and at least one or two rules to get into each routing
: table. I don't want to increase the number of routing tables if
: also increasing the number of rules on the box is going to do
: more harm than good.
I am not aware of any performance comparisons of typically routing
configurations against full RPDBs. It seems like you'd get some
benefit from your own sort of least recently used (LRU) sort before
inserting rules into the RPDB, though.
I hope somebody else out there will comment on:
- whether s/he is working on patches which would support up to
2 ** 16 routing tables (as opposed to 2 ** 8).
- performance metrics/routing comparison, Linux with one routing
table and a given load as against Linux with RPDB + many
routing tables
Good luck in getting your answer(s), Wayne,
- -Martin
[0] http://oss.sgi.com/archives/netdev/2005-08/msg00163.html
http://mailman.ds9a.nl/pipermail/lartc/2001q2/001073.html
http://mailman.ds9a.nl/pipermail/lartc/2004q1/011670.html
http://mailman.ds9a.nl/pipermail/lartc/2004q4/014125.html
http://mailman.ds9a.nl/pipermail/lartc/2005q4/017094.html
[1] http://marc.theaimsgroup.com/?l=linux-netdevm=115029279428349w=4
- --
Martin A. Brown
http://linux-ip.net/
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