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.
