Re: packet re-ordering on SMP machines.

[Ben Greear <greearb@candelatech.com>]

jamal wrote:

> That doesnt sound impressive at all. I know it's about .8 of wire rate
> but you should be able to exceed that.
> Robert was generating in the range of 800Kpps with that NIC if i recall
> corectly

I had only tested 1514 byte pkts, so I was getting around 880Mbps,
which is pretty good as far as I know.

I see about 255 kpps when sending 64 byte pkts to myself.  Still
dropping about 1 in 4000 packets at this speed.  I think most of Robert's
tests didn't involve actually doing something with the received packet
though, and I am inspecting it for latency, sequence number, etc.

I'm even doing a __get_timeofday() call to calculate the latency...need
to find a faster way to do that...

If I only allocate/scan 1 per 100 packets (ie alloc one packet and send it 100 times),
then I get a more respectable 365kpps.  Robert's patch should definately help!

> Also if you have SMP, tie each onto a CPU.

That's with the irq_afinity thing in proc, right?

> Additionaly get the skb recycler patch from Robert, it should improve
> things even more.

Do you happen to have a URL for this?

Actually, the various network tweaks are relatively hard to find
(at least to find the most up-to-date coppies).  It would be great if
there was a place where they were all concentrated.

> 
> 
>>Also, I see the hard_start_xmit call failing 5876 times out of 2719493
>>calls (for example).  The code that calls the method looks like this:
>>
> 
> 
> I dont have access to that NIC. But a stoopid question: Have you tried
> increasing the transmit queue via ifconfig? 1000 packets is reasonable
> for gige.

I upped it, but it didn't stop the errors.  The NIC is still performing,
so it may not be a real problem...

Thanks for the info,
Ben

-- 
Ben Greear <greearb@candelatech.com>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear