On Tue, 3 Jun 2014 04:36:07 -0400
"Chen, Gong" [off-list ref] wrote:

On Mon, Jun 02, 2014 at 12:57:48PM -0400, Steven Rostedt wrote:

quoted

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?

You can create a helper function to call (needs to be placed in a .c
file).

Note, there's a pointer to a trace_seq structure "p" that is available.
Hmm, I should add a get_dynamic_array_len(field), to give you the
length. I'll add that now. I also don't like the trace_seq being "p" as
that is too generic. Maybe I'll change that to "__trace_seq" or
something not so generic.


Anyway, have something like this:


	TP_printk("%s", emca_parse_events(p, __get_dynamic_array(field),
			__get_dynamic_array_len(field)));

I'll still need to add that __get_dynamic_array_len() helper. I'll send
you something tonight.

Then you write the emca_parse_events() as:


const char *emca_parse_events(struct trace_seq *p,
		struct cper_sec_mem_rec *data, int len)
{
	const char *ret = p->buffer + p->len;
	int i;

	len = len / sizeof(struct cper_sec_mem_rec);
	for (i = 0; i < len; i++) {
		switch (data[i].type) {
		case FOO:
			trace_seq_printf(p, "BAR: %d\n", data[i].data);
			break;
		[..]
		}
	}
	trace_seq_putc('\0');

	return ret;
}

-- Steve