Michael Tasche
|
Re: RE: local UDP Echo test three times slower on QNX than on Linux
|
Michael Tasche
01/31/2009 4:36 PM
post21193
|
Re: RE: local UDP Echo test three times slower on QNX than on Linux
Hi Robert,
> Hi Malte:
>
> I've spent some time looking into this and need a bit of feedback. I've
> got two 2.1 GHz dual core Intel boxes with Intel GigE (PCI Express
> cards) in them. I've got them dual booting Ubuntu 8.04 and Neutrino
> 6.4.0.
>
> I slightly modified the udpcli.c to time the series command (i.e. print
> out the amount of time it takes to do the given number of series instead
> of doing a histogram).
>
> On Neutrino, localhost gives me (for 100,000 reps) ~2.2 s as compared to
> ~1.2 seconds for Linux... This is less than a factor of 2 which is not
> bad (but we still have to do the analysis to figure out where the time
> is going).
>
> The really interesting thing is what happens when you try the same
> application using real hardware instead of over localhost. With the new
> version of devnp-i82544 that we have, if you run the stack on both sides
> with
>
> io-pkt-v4 -di82544 irq_thresh=0
>
> 100000 reps takes 8.6 seconds. The same hardware on linux is giving me
> 10.6 seconds, so we're 25% faster than Linux in this case.
>
> Is there anyway that you can confirm this? I suspect that this will be
> HIGHLY dependent upon the driver...
I think you are right, the driver is the most important key.
Some of our QNX embedded targets are very very slow on the network.
The actual network drivers for ppc405gpr, ppc440epx and mpc5200 are far away from optimized drivers. If I remember right
, the main problem is the tx-path of those drivers. The TX-packets are defragmented/copied by the cpu before they will
fetched by the dma-part oft the network chips. Additionally there seems to be annother strange problem in the mpc5200-
driver, which transfers more bytes/sec as "echo server" than as "chargen server" !?
Well, these drivers are stable and do not make problems in a hard realtime environment, were some important threads live
above the io-pkt priority.
Perhaps the native ports of these drivers will get faster in the future.
Kind Regards
Michael
>
> Robert.
>
>
>
> -----Original Message-----
> From: Malte Mundt [mailto:community-noreply@qnx.com]
> Sent: Monday, January 26, 2009 9:34 AM
> To: technology-networking
> Subject: Re: local UDP Echo test three times slower on QNX than on Linux
>
> The kernel trace log. It clearly shows io-pkt being very busy, and also
> it seems the client wakes up a 2nd time before the server processes the
> first echo, not sure if my interpretation is correct though.
>
> _______________________________________________
> Technology
> http://community.qnx.com/sf/go/post20779
|
|
|