[PATCH v9 5/5] eal: add option to put timestamp on console output

[Morten Brørup]

> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Wednesday, 20 March 2024 04.34
> 
> On Tue, 19 Mar 2024 17:13:35 +0100
> Morten Brørup <mb at smartsharesystems.com> wrote:
> 
> > > From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> > > Sent: Tuesday, 19 March 2024 16.52
> > >
> > > On Tue, 19 Mar 2024 08:37:30 +0100
> > > Morten Brørup <mb at smartsharesystems.com> wrote:
> > >
> > > > >  static ssize_t
> > > > >  console_log_write(__rte_unused void *c, const char *buf, size_t
> > > size)
> > > > >  {
> > > > > +	struct timespec ts;
> > > > >  	ssize_t ret;
> > > > >
> > > > > -	/* write on stderr */
> > > > > -	ret = fwrite(buf, 1, size, stderr);
> > > > > +	if (timestamp_enabled) {
> > > > > +		clock_gettime(CLOCK_MONOTONIC, &ts);
> > > > > +		ts.tv_sec -= log_started.tv_sec;
> > > > > +		ts.tv_nsec -= log_started.tv_nsec;
> > > >
> > > > Please log the absolute CLOCK_MONOTONIC instead of subtracting
> > > log_started, so timestamps can be easily compared with timestamps from
> > > other processes.
> > >
> > >
> > > No, was trying to do what kernel dmesg does.
> >
> > What do you mean? Doesn't the kernel output CLOCK_MONOTONIC timestamps
> (without offset)?
> >
> > And by "timestamps from other processes" I also mean timestamps in log
> messages from the kernel itself.
> >
> 
> If you look at dmesg command that formats the messages, it has lots of
> timestamp options.
> Next version will support more of these.
> 
>        --time-format format
>            Print timestamps using the given format, which can be ctime,
>            reltime, delta or iso. The first three formats are aliases of
>            the time-format-specific options. The iso format is a dmesg
>            implementation of the ISO-8601 timestamp format. The purpose
>            of this format is to make the comparing of timestamps between
>            two systems, and any other parsing, easy. The definition of
>            the iso timestamp is:
>            YYYY-MM-DD<T>HH:MM:SS,<microseconds>←+><timezone offset from
>            UTC>.

That's formatting.

I'm talking about the initial offset.

The kernel's "log start time" is set to system start timestamp.

Your "log start time" is set to application start timestamp:

+void
+eal_log_enable_timestamp(void)
+{
+	timestamp_enabled = true;
+	clock_gettime(CLOCK_MONOTONIC, &log_started);
+}

So, different offset. I prefer using the same offset.