netmap overrun counters

[bazzoola]

On 04/28/2016 12:06 PM, Luigi Rizzo wrote:
> 
> 
> On Thursday, April 28, 2016, bazzoola <bazzoola at gmail.com
> <mailto:bazzoola at gmail.com>> wrote:
> 
> 
> 
>     On 04/28/2016 11:35 AM, Navdeep Parhar wrote:
>     > On 04/28/2016 11:13, bazzoola wrote:
>     >> Hi!
>     >>
>     >> Two questions:
>     >>
>     >> (1) Is there a way to know when netmap rx rings overrun? Most NIC
>     >> drivers provide MPC (missed packet count) and sysctl for rx_overrun.
>     >>
>     >> I would like to know if my application is not reading as fast,
>     i.e., no
>     >> frames are being dropped.
>     >
>     > A NIC's hardware counters don't distinguish between netmap or normal
>     > operation so you can monitor the existing sysctls for rx
>     drops/overruns.
>     >
>     > Regards,
>     > Navdeep
>     >
> 
>     Navdeep,
> 
>     I am not asking about NIC's ring overrun. As you know netmap has its own
>     rings. Is there a way to know if netmap's rx ring overrun?
> 
> 
> Overruns by definition can only be counted by the NIC
> 
> Cheers
> Luigi
>  
> 

Luigi,

I will rephrase the question to avoid the 'overrun' definition.

(1) if my application is not reading fast enough is there a way to know
if netmap's rx ring starts overwriting unread slots?

Also, my section question was:

(2) What is the benefit of NETMAP_DO_RX_POLL? I do see the slots being
updated when I set this flag but 'tail' is not advancing unless I read.

Basically, all I am trying to do is detect if frames are dropped in my
application using netmap API.

Thanks!

B.