Evgeniy Polyakov a e'crit :
On Mon, Feb 05, 2007 at 10:02:53AM -0800, [EMAIL PROTECTED] ([EMAIL PROTECTED])
wrote:
On Sat, 4 Feb 2007 [EMAIL PROTECTED] wrote:
I noticed in an LCA talk mention that apprently extensible hashing
with RCU access is an unsolved problem. Here's an idea for solving it.
....
Yes, I have been playing around with the same idea for
doing dynamic resizing of the TCP hashtable.
Did a prototype "toy" implementation, and I have a
"half-finished" patch which resizes the TCP hashtable
at runtime. Hmmm, your mail may be the impetus to get
me to finally finish this thing....
Why anyone do not want to use trie - for socket-like loads it has
exactly constant search/insert/delete time and scales as hell.
Because we want to be *very* fast. You cannot beat hash table.
Say you have 1.000.000 tcp connections, with 50.000 incoming packets per
second to *random* streams...
With a 2^20 hashtable, a lookup uses one cache line (the hash head pointer)
plus one cache line to get the socket (you need it to access its refcounter)
Several attempts were done in the past to add RCU to ehash table (last done by
Benjamin LaHaise last March). I believe this was delayed a bit, because
David would like to be able to resize the hash table...
I am not really interested in hash resizing, because an admin can size it at
boot time. But RCU is definitly *wanted*
Note : It would be good to also use RCU for UDP, because the current rwlock
protecting udp_hash[] is a scalability problem.
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