Re: [PATCH v28 0/8] Timestamp synchronization of host - guest tracing session

[Dario Faggioli <dfaggioli@suse.com>]

[-- Attachment #1: Type: text/plain, Size: 1847 bytes --]

On Wed, 2021-02-10 at 16:59 -0500, Steven Rostedt wrote:
> On Tue, 09 Feb 2021 13:24:23 +0100
> Dario Faggioli <dfaggioli@suse.com> wrote:
> > 
> > == VM:
> > # echo tsc >
> > /sys/devices/system/clocksource/clocksource0/current_clocksource
> > # echo x86-tsc > /sys/kernel/tracing/trace_clock
> > # trace-cmd agent
> > 
> > == Host:
> > # echo x86-tsc > /sys/kernel/tracing/trace_clock
> > # trace-cmd record -p nop -e sched:* -e kvm:* -e timer:hrtimer* -A
> > tumbleweed-jeos:823 -e sched:* -e syscalls:*_clock_nanosleep -e
> > timer:hrtimer* sleep 1
> > 
> 
> Note you can use -C x86-tsc on the command line which would handle
> the
> clocks for you. I believe it may update the agent as well, but if
> not, you
> can add it to the agent as well. Also "-p nop" shouldn't be needed,
> as that
> would happen automatically if "-p" is left off.
> 
>  trace-cmd record -e sched -e kvm -e 'hrtimer*' -C x86-tsc \
>    -A tumbleweed-jeos:823 -e sched -e '*_clock_nanosleep' -e
> 'hrtimer*' \
>    sleep 1
> 
Right. That's better indeed.

> > And I do end up with the two files: trace.dat for the host and
> > trace-
> > (null).dat (oh, well :-D) for the guest.
> 
> I believe my latest push should fix that ;-)
> 
Yes, 27c464a74f8f54d0 (trace-cmd: Use instance->name for guests and not
tracefs instance name) fixes this for me.

I was also trying to do some debugging, out of curiosity. And in fact I
was not understanding where the name was being copied in the place
where tracefs_instance_get_name() looks for it. :-)

Thanks!
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 833 bytes --]