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more TODO stuff

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Brendan O'Dea 2004-07-12 08:19:46 +00:00
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commit 6e1e4432fc
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@ -223,3 +223,43 @@ TODO:
a packet from a non-existant session then forward it to the master??
In normal practice, a slave with undefined session shouldn't be
handling packets, but ...
There is far too much walking of large arrays (in the master
specifically). Although this is mitigated somewhat by the
cluster_high_{sess,tun}, this benefit is lost as that value gets
closer to MAX{SESSION,TUNNEL}. There are two issues here:
* The tunnel, radius and tbf arrays should probably use a
mechanism like sessions, where grabbing a new one is a
single lookup rather than a walk.
* A list structure (simillarly rooted at [0].interesting) is
required to avoid having to walk tables periodically. As a
back-stop the code in the master which *does* walk the
arrays can mark any entry it processes as "interesting" to
ensure it gets looked at even if a bug causes it to be
otherwiase overlooked.
Support for more than 64k sessions per cluster. There is
currently a 64k session limit because each session gets an id that global
over the cluster (as opposed to local to the tunnel). Obviously, the tunnel
id needs to be used in conjunction with the session id to index into
the session table. But how?
I think the best way is to use something like page tables.
for a given <tid,sid>, the appropriate session index is
session[ tunnel[tid].page[sid>>10] + (sid & 1023) ]
Where tunnel[].page[] is a 64 element array. As a tunnel
fills up it's page block, it allocated a new 1024 session block
from the session table and fills in the appropriate .page[]
entry.
This should be a reasonable compromise between wasting memory
(average 500 sessions per tunnel wasted) and speed. (Still a direct
index without searching, but extra lookups required). Obviously
the <6,10> split on the sid can be moved around to tune the size
of the page table v the session table block size.
This unfortunately means that the tunnel structure HAS to
be filled on the slave before any of the sessions on it can be used.