Re: Sporadic errors while initializing NICs in example applications, dpdk-1.5.0r1

[Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>]

29/11/2013 14:53, Dmitry Vyal :
> On 11/28/2013 03:01 PM, Richardson, Bruce wrote:
> >> It's probably due to a frequency scaling.
> >> The timer based is initialized when DPDK initialize and the CPU can
> >> change
> >> its frequency, breaking next timers.
> >> 
> >> The fix is to control the CPU frequency.
> >> 
> >> Please try this, without your patch:
> >> 	for g in /sys/devices/system/cpu/*/cpufreq/scaling_governor; do
> >> 
> >> echo performance >$g; done The right fix for applications (examples and
> >> testpmd included) could be to call rte_power_init(). Patches are
> >> welcomed.
> > 
> > [BR] Frequency changes should not affect timers for modern Intel CPUs.
> > Please see the " Intel(r) 64 and IA-32 Architectures Software Developer's
> > Manual" Volume 3
> > (http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-i
> > a-32-architectures-software-developer-system-programming-manual-325384.pdf
> > ) , Section 17.13 for more details on this.
>
> Hmm, that's strange. I don't know how to interpret my observations then.
> I have access to two platforms, one is based on Intel(R) Xeon(R) CPU
> E3-1230 V2 @ 3.30GHz and another on Intel(R) Xeon(R) CPU E3-1270 v3 @
> 3.50GHz. Both running ubuntu-12.04 server. I see repeating errors on NIC
> initialisation phase. The error frequency greatly reduces if I patch
> loop limit as I described earlier or if I call rte_power_init and
> rte_power_freq_max as Thomas suggested.
>
> But the only way to get rid of them completely is to set performance
> governor.

Please check that your hardware do not support invariant TSC.
It would explain why you need to fix frequency.

I attach a simple code to test CPU feature "Invariant TSC".

-- 
Thomas