How to display a ktime value as trace timestamp in trace output?

How to display a ktime value as trace timestamp in trace output?

[David Howells]

Hi Steven,

I have a tracepoint in AF_RXRPC that displays information about a timeout I'm
going to set.  I have the timeout in a ktime_t as an absolute time.  Is there
a way to display this in the trace output such that it looks like a trace
timestamp and can be (roughly) correlated with the displayed timestamps?

I tried subtracting ktime_get_read() - ktime_get_boottime() from it and
displaying the result, but it looked about one and a bit seconds out from the
trace timestamp.

Thanks,
David

Re: How to display a ktime value as trace timestamp in trace output?

[Steven Rostedt]

On Wed, 31 Jan 2024 14:47:31 +0000
David Howells <dhowells@redhat.com> wrote:

> Hi Steven,

Hi David,

Sorry, I just noticed this email as it was buried in other unread emails :-p

> 
> I have a tracepoint in AF_RXRPC that displays information about a timeout I'm
> going to set.  I have the timeout in a ktime_t as an absolute time.  Is there
> a way to display this in the trace output such that it looks like a trace
> timestamp and can be (roughly) correlated with the displayed timestamps?

Have you tried the other clocks?

	{ ktime_get_mono_fast_ns,	"mono",		1 },
	{ ktime_get_raw_fast_ns,	"mono_raw",	1 },
	{ ktime_get_boot_fast_ns,	"boot",		1 },

The above are the functions used for the tracing timestamps.

-- Steve

> 
> I tried subtracting ktime_get_read() - ktime_get_boottime() from it and
> displaying the result, but it looked about one and a bit seconds out from the
> trace timestamp.
>