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List:       freebsd-hackers
Subject:    Re: high CPU usage in FreeBSD for a PCIe card driver
From:       Steevan Rodrigues <steevanxperia () gmail ! com>
Date:       2018-07-11 23:57:41
Message-ID: CAKsGTHSj3cgQML1bEJ7UdQdFcF1hfbvq51yS2U2bBE8Vc8rR1Q () mail ! gmail ! com
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Thanks for confirming it.  Yes I do very frequent device ioctl calls .

Regards,
Steevan

On Wed, Jul 11, 2018 at 11:52 PM, Andrew Gallatin <gallatin@cs.duke.edu>
wrote:

> 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
>
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