high CPU usage in FreeBSD for a PCIe card driver

[Andrew Gallatin]

On 07/11/18 07:46, Steevan Rodrigues wrote:
> Hello Andrew,
> 
> Sorry to bother you.  I am working on this problem again after a break 
> of few days.
> I ran following command  to get lock statistics  when I run my userspace 
> application on a 12 core 24 thread server PC.
>  From this data below  to looks like my driver is causing a contention 
> on a kernel lock  (pmap ).  Am I right ?
> 
>   lockstat -x aggsize=4m -D 20 sleep 10
> 
> Adaptive mutex spin: 1122679 events in 10.013 seconds (112121 events/sec)
> 
> Count indv cuml rcnt     nsec Lock                   Caller
> -------------------------------------------------------------------------------
> 1089662  97%  97% 0.00    65375 pmap                   pmap_extract+0x1d2
> 31805   3% 100% 0.00    14881 cdev                   devvn_refthread+0x142


Yes.  You can get more information if you use the -s 10 argument to 
lockstat.  That way, you'll see what's calling pmap_extract.

Are you doing frequent device ioctls?


Drew