Re: Q: dmesg: dt: 443 probes
Am Tue, May 04, 2021 at 03:38:14PM - schrieb Stuart Henderson: > On 2021-05-04, Why 42? The lists account. wrote: > > > > On Mon, May 03, 2021 at 12:59:27AM +0200, Patrick Wildt wrote: > >> > ... > >> > But when I do (as root): "sysctl kern.allowdt=1" it returns this error: > >> > sysctl: kern.allowdt: Operation not permitted > >> > >> Similarly to kern.allowkmem, you can only set it when the securelevel is > >> still 'low'. That's for security. You need to add kern.allowdt=1 to > >> sysctl.conf, and then reboot. Then it'll be enabled after reboot. > > > > Thanks Patrick! After the reboot I was able to experiment with btrace. > > > > Do you use it, do you have any examples that might help to get started? > > Here's one example: > https://marc.info/?l=openbsd-bugs=158583371404603=2 That's exactly the one I use. Though with varying hz (1-60)
Re: Q: dmesg: dt: 443 probes
On 2021-05-04, Why 42? The lists account. wrote: > > On Mon, May 03, 2021 at 12:59:27AM +0200, Patrick Wildt wrote: >> > ... >> > But when I do (as root): "sysctl kern.allowdt=1" it returns this error: >> > sysctl: kern.allowdt: Operation not permitted >> >> Similarly to kern.allowkmem, you can only set it when the securelevel is >> still 'low'. That's for security. You need to add kern.allowdt=1 to >> sysctl.conf, and then reboot. Then it'll be enabled after reboot. > > Thanks Patrick! After the reboot I was able to experiment with btrace. > > Do you use it, do you have any examples that might help to get started? Here's one example: https://marc.info/?l=openbsd-bugs=158583371404603=2
Re: Q: dmesg: dt: 443 probes
On Mon, May 03, 2021 at 12:59:27AM +0200, Patrick Wildt wrote:
> > ...
> > But when I do (as root): "sysctl kern.allowdt=1" it returns this error:
> > sysctl: kern.allowdt: Operation not permitted
>
> Similarly to kern.allowkmem, you can only set it when the securelevel is
> still 'low'. That's for security. You need to add kern.allowdt=1 to
> sysctl.conf, and then reboot. Then it'll be enabled after reboot.
Thanks Patrick! After the reboot I was able to experiment with btrace.
Do you use it, do you have any examples that might help to get started?
Using the bfptrace reference guide:
https://github.com/iovisor/bpftrace/blob/master/docs/reference_guide.md
I was able to get a simple "Hello World" to run, but more than that
seemed to cause me some problems e.g.
> # btrace -e 'BEGIN{ @enq = 0 } tracepoint:sched:enqueue { @enq = @enq + 1; }
> interval:s:10 { printf("sched_enqueue: %d\n", @enq) ; @enq = 0; }'
> btrace:1:77: syntax error:
> BEGIN{ @enq = 0 } tracepoint:sched:enqueue { @enq = @enq + 1; } interval:s:10
> { printf("sched_enqueue: %d\n", @enq) ; @enq = 0; }
> ^
Doesn't seem to like the interval syntax?
Or this one which does run but then takes an assertion failure:
> # btrace -e 'BEGIN{ @enq = 0 } tracepoint:sched:enqueue { @enq =
> lhist(retval, 0, 1000, 100); }'
> assertion "hist->hstep == step" failed: file
> "/usr/src/usr.sbin/btrace/map.c", line 246, function "hist_increment"
> zsh: abort (core dumped) btrace -e
Thanks again in any case!
Cheers,
Robb.
Re: Q: dmesg: dt: 443 probes
Am Sun, May 02, 2021 at 11:49:10PM +0200 schrieb Why 42? The lists account.: > > Actually I do notice one thing, having just upgraded to: > kern.version=OpenBSD 6.9-current (GENERIC.MP) #492: Sat May 1 17:37:28 MDT > 2021 > > I checked the output from dmesg and I have a new boot time message: > dt: 443 probes > > man dt tells me that dt is dynamic tracing and that I can enable it by > setting kern.allowdt. > > But when I do (as root): "sysctl kern.allowdt=1" it returns this error: > sysctl: kern.allowdt: Operation not permitted Similarly to kern.allowkmem, you can only set it when the securelevel is still 'low'. That's for security. You need to add kern.allowdt=1 to sysctl.conf, and then reboot. Then it'll be enabled after reboot. > What am I missing? > > Cheers, > Robb. > > FYI: This is on an Intel NUC: > bios0 at mainbus0: SMBIOS rev. 3.2 @ 0x7a9a4000 (77 entries) > bios0: vendor Intel Corp. version "BECFL357.86A.0087.2020.1209.1115" date > 12/09/2020 > bios0: Intel(R) Client Systems NUC8i5BEH >
Q: dmesg: dt: 443 probes
Actually I do notice one thing, having just upgraded to: kern.version=OpenBSD 6.9-current (GENERIC.MP) #492: Sat May 1 17:37:28 MDT 2021 I checked the output from dmesg and I have a new boot time message: dt: 443 probes man dt tells me that dt is dynamic tracing and that I can enable it by setting kern.allowdt. But when I do (as root): "sysctl kern.allowdt=1" it returns this error: sysctl: kern.allowdt: Operation not permitted What am I missing? Cheers, Robb. FYI: This is on an Intel NUC: bios0 at mainbus0: SMBIOS rev. 3.2 @ 0x7a9a4000 (77 entries) bios0: vendor Intel Corp. version "BECFL357.86A.0087.2020.1209.1115" date 12/09/2020 bios0: Intel(R) Client Systems NUC8i5BEH
