Re: Some performance measurements on the FreeBSD network stack

On Thu, Apr 19, 2012 at 11:22 PM, Luigi Rizzo <rizzo_at_iet.unipi.it> wrote:
> On Thu, Apr 19, 2012 at 10:34:45PM +0200, K. Macy wrote:
>> >> This is indeed a big problem. ?I'm working (rough edges remain) on
>> >> changing the routing table locking to an rmlock (read-mostly) which
>> >
>>
>> This only helps if your flows aren't hitting the same rtentry.
>> Otherwise you still convoy on the lock for the rtentry itself to
>> increment and decrement the rtentry's reference count.
>>
>> > i was wondering, is there a way (and/or any advantage) to use the
>> > fastforward code to look up the route for locally sourced packets ?
>
> actually, now that i look at the code, both ip_output() and
> the ip_fastforward code use the same in_rtalloc_ign(...)
>
>> >
>>
>> If the number of peers is bounded then you can use the flowtable. Max
>> PPS is much higher bypassing routing lookup. However, it doesn't scale
>> to arbitrary flow numbers.
>
> re. flowtable, could you point me to what i should do instead of
> calling in_rtalloc_ign() ?

If you build with it in your kernel config and enable the sysctl
ip_output will automatically use it for TCP and UDP connections. If
you're doing forwarding you'll need to patch the forwarding path.
Fabien Thomas has a patch for that that I just fixed/identified a bug
in for him.

-Kip


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