netdev - Re: state of rtcache removal...

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Message-Id: <20110216.192751.104051014.davem@davemloft.net>
Date:	Wed, 16 Feb 2011 19:27:51 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	therbert@...gle.com
Cc:	netdev@...r.kernel.org
Subject: Re: state of rtcache removal...

From: Tom Herbert <therbert@...gle.com>
Date: Wed, 16 Feb 2011 18:59:35 -0800

> On Wed, Feb 16, 2011 at 4:08 PM, David Miller <davem@...emloft.net> wrote:
>>
>> So I've been testing out the routing cache removal patch to see
>> what the impact is on performance.
>>
> Interesting results.
> 
> I assume that this test is purposely using sento on a connected socket
> to force sendmsg to go through the route lookup :-), so this is
> showing what the benefits of rtcache are is when cache hit rate is
> 100%.  For comparison, it might interesting to see what the
> performance is when rate is < 100%.  For instance, we often see hit
> rates < 20% on front end servers.  This could be done flooding to
> random addresses in 10/8 or even 0/0...  I'm hoping that without the
> rtcache performance actually improves in that case!

We know that the performance will be higher in the "closer to %0"
situation, ie.  for DoS workloads.  Because all of the route cache
management overhead goes away.

Anyways I'm working on some ideas to make the high hit rate case
perform amicably again.
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