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Date: Tue, 23 Jan 2024 09:49:00 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Huang Yiwei <quic_hyiwei@quicinc.com>
Cc: <mhiramat@kernel.org>, <mark.rutland@arm.com>, <mcgrof@kernel.org>,
 <keescook@chromium.org>, <j.granados@samsung.com>,
 <mathieu.desnoyers@efficios.com>, <corbet@lwn.net>,
 <linux-kernel@vger.kernel.org>, <linux-trace-kernel@vger.kernel.org>,
 <linux-fsdevel@vger.kernel.org>, <linux-doc@vger.kernel.org>,
 <quic_bjorande@quicinc.com>, <quic_tsoni@quicinc.com>,
 <quic_satyap@quicinc.com>, <quic_aiquny@quicinc.com>, <kernel@quicinc.com>,
 Ross Zwisler <zwisler@google.com>, Joel Fernandes <joel@joelfernandes.org>
Subject: Re: [PATCH v3] tracing: Support to dump instance traces by
 ftrace_dump_on_oops
Message-ID: <20240123094900.6f96572c@gandalf.local.home>
In-Reply-To: <0279a4cb-ced0-447a-a06f-37c38650ed5b@quicinc.com>
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On Tue, 23 Jan 2024 18:23:58 +0800
Huang Yiwei <quic_hyiwei@quicinc.com> wrote:

> > And if we really want to be fancy!
> > 
> > 	ftrace_dump_on_opps[=orig_cpu | =<instance> | =orig_cpu:<instance> ][,<instance> | ,<instance>:orig_cpu]
> >   
> Yeah, I agree to make the parameter more flexible.
> 
> "=orig_cpu:<instance>" means to dump global and another instance?

No, I added a comma for that:

  =,orig_cpu:<instance>

Would mean to dump all of global and just the origin CPU of the instance.

> 
> I'm thinking of the following format:
> 
> ftrace_dump_on_opps[=orig_cpu | =<instance>][,<instance> | 
> ,<instance>=orig_cpu]
> 
> Here list some possible situations:
> 
> 1. Dump global on orig_cpu:
> ftrace_dump_on_oops=orig_cpu
> 
> 2. Dump global and instance1 on all cpu, instance2 on orig_cpu:
> ftrace_dump_on_opps,<instance1>,<instance2>=orig_cpu
> 
> 3. Dump global and instance1 on orig_cpu, instance2 on all cpu:
> ftrace_dump_on_opps=orig_cpu,<instance1>=orig_cpu,<instance2>
> 
> 4. Dump instance1 on all cpu, instance2 on orig_cpu:
> ftrace_dump_on_opps=<instance1>,<instance2>=orig_cpu
> 
> 5. Dump instance1 and instance2 on orig_cpu:
> ftrace_dump_on_opps=<instance1>=orig_cpu,<instance2>=orig_cpu
> 
> This makes orig_cpu dump for global same as instance, the parameter may 
> seems more unified and users don't need to remember another markers to 
> request orig_cpu dump.
> 
> But one problem here is if there's an instance named "orig_cpu", then we 
> may not dump it correctly.

I would put that under:

   Patient: Doctor it hurts me when I do this
   Doctor:  Then don't do that

;-)

-- Steve