high CPU usage in FreeBSD for a PCIe card driver

[Steevan Rodrigues]

Thank you so much for the suggestions .  I will use these commands.
Yes, I am already working on to identify lock contentions.

Re-built FreeBSD kernel by enabling lock profiling and  now I am able to
see some issues with contention.

Thanks
Steevan

On Thu, Jun 28, 2018 at 6:34 PM, Andrew Gallatin <gallatin at cs.duke.edu>
wrote:

> On 06/27/18 08:28, Steevan Rodrigues wrote:
>
>> Hi
>>
>> I  come from Linux background and new to FreeBSD.
>>
>> I am investigating a high CPU usage issue on FreeBSD for PCIe driver of a
>>
>
> <...>
>
>
>> I wonder whether usage of mtx_lock is the cause of high CPU usage ? Any
>> pointers or suggestions welcome.
>>
>
>
> It seems like you're experiencing lock contention.  The next step is to
> determine which lock is contended and why.
>
> I would suggest using the lockstat program to identify the lock which
> is contended.  Try this:  lockstat -x aggsize=4m sleep 10 > out
>
> And this:  lockstat -x aggsize=4m -s 10 sleep 10 > out-stacks
>
> The first will show you contended locks broken down by type.  Eg:
>
>
> Adaptive mutex spin: 61262 events in 10.007 seconds (6122 events/sec)
>
> Count indv cuml rcnt     nsec Lock                   Caller
> ------------------------------------------------------------
> -------------------
> 15958  26%  26% 0.00     2960 tcp_hpts_lck           __tcp_hpts_remove+0xb5
> 11723  19%  45% 0.00     2608 tcp_hpts_lck tcp_hpts_insert_diag+0xaf
>  6903  11%  56% 0.00     4605 tcp_hpts_lck           tcp_hpts_thread+0x11e
>  6834  11%  68% 0.00   125868 sleep mtxpool          _sleep+0x2e3
>  2756   4%  72% 0.00     1530 vm page sendfile_free_page+0x1c1
>
>
> The second will show you the stacks associated with the lock contention,
> and may help you identify the source of contention if, for example, your
> driver is causing contention on a kernel lock.
>
> Drew
>
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