linux-kernel - Re: [PATCH 5/7 v6] trace, RAS: Add eMCA trace event interface

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Date:	Tue, 3 Jun 2014 04:36:07 -0400
From:	"Chen, Gong" <gong.chen@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"Luck, Tony" <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
	"m.chehab@...sung.com" <m.chehab@...sung.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7 v6] trace, RAS: Add eMCA trace event interface

On Mon, Jun 02, 2014 at 12:57:48PM -0400, Steven Rostedt wrote:
> Also matters how big you expect these events to be. If you get a
> "christmas tree" set of flags, how big will that event grow with all
> the descriptions attached?
> 
> The max event size after all headers is 4056 bytes. If you go over
> that, the event is ignored.
> 
Hi, Steven

Normally, the length of one eMCA trace record is between 200 and 256 bytes.
Once CMCI storm happens, before it is turned into poll mode, there are
about ~15 CMCI events are recorded, because I don't use rate limit for
trace so they should be recorded so seriously, some records will be lost.
But they are repeated and similar records so maybe the *lost* is not a 
big issue.

Return to how to print trace record. To avoid buffer waste, I need to
print data when TP_printk called, in the meanwhile, the print content
is an array of [name, value], but we don't know how many items are
valid. Here is the question: I can't create a dynamic printk format
like "%s %d, %s %d, ..." in TP_printk. So the only way to me is
printking them all, even some of them are invalid, which means an 12
group "%s %d", or somthing like "%.*s" to make output format graceful.
This is what we want?

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