Hi James,

On Thu, Apr 15, 2021 at 03:51:46PM +0300, James Clark wrote:

[...]

quoted

For the orignal perf data file with "--per-thread" option, the decoder
runs into the condition for "etm->timeless_decoding"; and it doesn't
contain ETM timestamp.

Afterwards, the injected perf data file also misses ETM timestamp and
hit the condition "etm->timeless_decoding".

So I am confusing why the original perf data can be processed properly
but fails to handle the injected perf data file.

Hi Leo,

My patch only deals with per-cpu mode. With per-thread mode everything is already working
because _none_ of the events have timestamps because they are not enabled by default:

	/* In per-cpu case, always need the time of mmap events etc */
	if (!perf_cpu_map__empty(cpus))
		evsel__set_sample_bit(tracking_evsel, TIME);

When none of the events have timestamps, I think perf doesn't use the ordering code in
ordered-events.c. So when the inject file is opened, the events are read in file order.

The explination makes sense to me.  One thinking: if the original file
doesn't use the ordered event, is it possible for the injected file to
not use the ordered event as well?

Could you confirm Intel-pt can work well for per-cpu mode for inject
file?

So it's not really about --per-thread vs per-cpu mode, it's actually about whether
PERF_SAMPLE_TIME is set, which is set as a by-product of per-cpu mode.

I hope I understood your question properly.

Thanks for info, sorry if I miss any info you have elaborated.

Leo

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