Re: Some performance measurements on the FreeBSD network stack

From: K. Macy <kmacy_at_freebsd.org>
Date: Thu, 19 Apr 2012 23:17:41 +0200
>> 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.
>
>
> The rtentry lock isn't obtained anymore.  While the rmlock read
> lock is held on the rtable the relevant information like ifp and
> such is copied out.  No later referencing possible.  In the end
> any referencing of an rtentry would be forbidden and the rtentry
> lock can be removed.  The second step can be optional though.

Can you point me to a tree where you've made these changes?

>>> 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 ?
>>>
>>
>> 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.
>
>
> In theory a rmlock-only lookup into a default-route only routing
> table would be faster than creating a flow table entry for every
> destination.  It a matter of churn though.  The flowtable isn't
> lockless in itself, is it?

It is. In a steady state where the working set of peers fits in the
table it should be just a simple hash of the ip and then a lookup.

-Kip
-- 
   “The real damage is done by those millions who want to 'get by.'
The ordinary men who just want to be left in peace. Those who don’t
want their little lives disturbed by anything bigger than themselves.
Those with no sides and no causes. Those who won’t take measure of
their own strength, for fear of antagonizing their own weakness. Those
who don’t like to make waves—or enemies.

   Those for whom freedom, honour, truth, and principles are only
literature. Those who live small, love small, die small. It’s the
reductionist approach to life: if you keep it small, you’ll keep it
under control. If you don’t make any noise, the bogeyman won’t find
you.

   But it’s all an illusion, because they die too, those people who
roll up their spirits into tiny little balls so as to be safe. Safe?!
>From what? Life is always on the edge of death; narrow streets lead to
the same place as wide avenues, and a little candle burns itself out
just like a flaming torch does.

   I choose my own way to burn.”

   Sophie Scholl
Received on Thu Apr 19 2012 - 19:17:42 UTC

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