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Re: Route cache performance under stress

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: Route cache performance under stress
From: Robert Olsson <Robert.Olsson@xxxxxxxxxxx>
Date: Tue, 10 Jun 2003 21:53:33 +0200
Cc: Robert.Olsson@xxxxxxxxxxx, ralph+d@xxxxxxxxx, ralph@xxxxxxxxx, hadi@xxxxxxxxxxxxxxxx, xerox@xxxxxxxxxx, sim@xxxxxxxxxxxxx, fw@xxxxxxxxxxxxx, netdev@xxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx
In-reply-to: <20030610.115759.26513736.davem@xxxxxxxxxx>
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David S. Miller writes:

 > How did you "rip it out"?  Just never look into the routing
 > cache hash and never add entries there?  If so, then yes it is
 > excellent simulation for pure slow path.

 Look at the patch... 
 hash lookup is bypassed -> always slow path. no lookup in rt_intern_hash
 but we keep the entry in the hash and ip_rt_dst_alloc is changed to run
 do __rt_hash_shrink for each call.

 > This is not purely an algorithmic problem.  The highest cost thing we
 > do in the slow path of input route processing is source validation.
 > This requires real brains to eliminate.
 > Actually, that's a good idea, if someone if brave just rip out
 > fib_validate_source (just don't call it, should work for valid
 > traffic) and see what happens :)

 It should be easy to do... 


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