netdev - Re: [PATCH] net: allow netdev_wait

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Date:	Mon, 09 Aug 2010 11:03:18 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Benjamin LaHaise <bcrl@...et.ca>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Octavian Purdila <opurdila@...acom.com>,
	netdev@...r.kernel.org, Cosmin Ratiu <cratiu@...acom.com>
Subject: Re: [PATCH] net: allow netdev_wait_allrefs() to run faster

On 08/09/2010 10:48 AM, Benjamin LaHaise wrote:
> On Mon, Aug 09, 2010 at 10:44:14AM -0700, Ben Greear wrote:
>> We also have a few rules per interface, and notice that it takes around 10ms
>> per rule when we are removing them, even when using batching in 'ip':
> ...
>> Patrick thought had an idea, but I don't think he had time to
>> look at it further:
>>
>> "Its probably the synchronize_rcu() in fib_nl_delrule() and
>> the route flushing happening after rule removal."
>
> Yes, that would be a problem, but the issue is deeper than that -- if I'm
> not mistaken it's on the packet processing path that iptables doesn't scale
> for 100k interfaces with 1 rule per interface.  It's been a while since I
> ran the tests, but I don't think it's changed much.

It would be nice to tie the rules based on 'iif' to a specific
interface.  Seems it should give near constant time lookup for rules
if we only have a few per interface....

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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