Re: [PATCH v2 5/7] qla2xxx: Enhance driver tracing with separate tunable and more

[Himanshu Madhani <himanshu.madhani@oracle.com>]

> On Aug 29, 2022, at 9:59 AM, Arun Easi <aeasi@marvell.com> wrote:
> 
> Thanks for reviewing the code, Himanshu. Response inline..
> 
> On Mon, 29 Aug 2022, 9:24am, Himanshu Madhani wrote:
> 
>> Small nits
>> 
>>> On Aug 26, 2022, at 3:25 AM, Nilesh Javali <njavali@marvell.com> wrote:
>>> 
>>> From: Arun Easi <aeasi@marvell.com>
>>> 
>>> Older tracing of driver messages was to:
>>>   - log only debug messages to kernel main trace buffer AND
>>>   - log only if extended logging bits corresponding to this
>>>     message is off
>>> 
>>> This has been modified and extended as follows:
>>>   - Tracing is now controlled via ql2xextended_error_logging_ktrace
>>>     module parameter. Bit usages same as ql2xextended_error_logging.
>>>   - Tracing uses "qla2xxx" trace instance, unless instance creation
>>>     have issues.
>>>   - Tracing is enabled (compile time tunable).
>>>   - All driver messages, include debug and log messages are now traced
>>>     in kernel trace buffer.
>>> 
>>> Trace messages can be viewed by looking at the qla2xxx instance at:
>>>   /sys/kernel/tracing/instances/qla2xxx/trace
>>> 
>> ^^^^^^^^
>> This should be /sys/kernel/debug/tracing/instances/qla2xxx/trace
>> 
> 
> With tracefs, the location is moved to:
> 	/sys/kernel/tracing
> 
> ..with old location preserved.
> 

Okay got it... I think I got tripped by the nuance of tracefs to be mounted to see a new tracing directory to be populated.

Here’s what I had seen on my 6.0.0-rc1+ kernel,

I could not locate it at /sys/kernel/tracing instead old location which makes sense from the Documentation

root@tatoonie~6.0.0-rc1+:/# ls -l /sys/kernel/tracing/
total 0
root@tatoonie~6.0.0-rc1+:/# ls -l /sys/kernel/debug/tracing/instances/qla2xxx/trace
-rw-r----- 1 root root 0 Aug 29 08:54 /sys/kernel/debug/tracing/instances/qla2xxx/trace

maybe you can add a comment indicating tracefs should be mounted to see traces at 
/sys/kernel/tracing.

FYI.. you can also add 

Tested-by: Himanshu Madhani <himanshu.madhani@oracle.com>


> Regards,
> -Arun
> PS: # grep -A 10 '^The File System' Documentation/trace/ftrace.rst

-- 
Himanshu Madhani	Oracle Linux Engineering