From: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
To: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>,
christophe lombard <clombard@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Cc: Philippe Bergheaud <philippe.bergheaud@fr.ibm.com>,
"Alastair D'Silva" <alastair@linux.ibm.com>,
Christophe Lombard <christophe_lombard@fr.ibm.com>,
Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Subject: Re: [PATCH 2/3] cxl: Introduce module parameter 'enable_psltrace'
Date: Mon, 12 Feb 2018 14:54:45 +0100 [thread overview]
Message-ID: <51364d03-d7a5-471b-2531-cf4c17af8c8d@linux.vnet.ibm.com> (raw)
In-Reply-To: <87a7wf4flx.fsf@vajain21.in.ibm.com>
Le 11/02/2018 à 18:10, Vaibhav Jain a écrit :
> Thanks for reviewing the patch Christophe,
>
> christophe lombard <clombard@linux.vnet.ibm.com> writes:
>>> +bool cxl_enable_psltrace = true;
>>> +module_param_named(enable_psltrace, cxl_enable_psltrace, bool, 0600);
>>> +MODULE_PARM_DESC(enable_psltrace, "Set PSL traces on probe. default: on");
>>> +
>> I am not too agree to add a new parameter. This can cause doubts.
>> PSL team has confirmed that enabling traces has no impact.
>> Do you see any reason to disable the traces ?
>
> Traces on PSL follow a 'set and fetch' model. So once the trace buffer for
> a specific array is full it will stop and switch to 'FIN' state and at
> that point we need to fetch the trace-data and reinit the array to
> re-arm it.
If the PSL trace arrays don't wrap, is there anything to gain by
enabling tracing by default instead of letting the developer handle it
through sysfs? I was under the (now wrong) impression that the PSL would
wrap.
I'm not a big fan of the module parameter. It seems we're giving a
second way of activating traces on top of sysfs, more cumbersome and
limited.
Fred
> There might be some circumstances where this model may lead to confusion
> specifically when AFU developers assume that the trace arrays are
> already armed and dont re-arm it causing miss of trace data.
>
> So this module param is a compromise to keep the old behaviour of traces
> array intact where in the arming/disarming of the trace arrays is
> controlled completely by userspace tooling and not by cxl.
>
next prev parent reply other threads:[~2018-02-12 13:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-09 4:25 [PATCH 0/3] Provide ability to enable PSL traces on card probe Vaibhav Jain
2018-02-09 4:25 ` [PATCH 1/3] cxl: Introduce various enums/defines for PSL9 trace arrays Vaibhav Jain
2018-02-09 13:08 ` christophe lombard
2018-02-11 16:46 ` Vaibhav Jain
2018-02-09 4:25 ` [PATCH 2/3] cxl: Introduce module parameter 'enable_psltrace' Vaibhav Jain
2018-02-09 13:14 ` christophe lombard
2018-02-11 17:10 ` Vaibhav Jain
2018-02-12 10:46 ` christophe lombard
2018-02-12 13:54 ` Frederic Barrat [this message]
2018-02-13 11:07 ` Vaibhav Jain
2018-02-09 4:25 ` [PATCH 3/3] cxl: Provide implementation for sl_ops.start_psltrace on PSL9 Vaibhav Jain
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