Dear Thomasz and Ben,
Many thanks for the explanation. I can confirm that the workaround is
effective. (In hindsight the man page has somewhat documented this
behavior under the ``--kernel'' flag.)
The only thing I have to add is that an edit to this part of the man
page may be in order:
Unless tiptop is run by root, or the executable is setuid-root, a user can only
monitor the tasks it owns.
I don't think adding the workaround to the man page is necessary, but it
would be good to know that by default tiptop requires root to monitor
any tasks at all.
Also, if upstream is amenable, a more specific error message would be great.
Cheers,
Nathaniel
On 05/15/2017 01:35 AM, Tomasz Buchert wrote:
On 14/05/17 20:58, Ben Hutchings wrote:
On Sun, 2017-05-14 at 10:43 +0200, Tomasz Buchert wrote:
On 12/05/17 18:54, Nathaniel Beaver wrote:
[...]
Thank you, Nathaniel.
I confirm the problem. A safe bet is that
https://lkml.org/lkml/2016/1/11/587 is the cause. You can verify that
/proc/sys/kernel/perf_event_paranoid contains "3". By running
echo 2 | sudo tee /proc/sys/kernel/perf_event_paranoid
you should be able to use tiptop as a normal user again.
I doubt that we can switch the default value in Debian kernels to "2",
so I have to say that simply the tiptop website is not up-to-date, at
least with respect to the Debian kernels (but also likely to other
distributions as well). I'm CCing Ben to let him comment on this.
The Debian kernel default is not going to be changed in the short term.
In the long term it's conceivable that performance events will
eventually become sufficiently robust that it would be reasonable to
change the default.
Ben.
--
Ben Hutchings - Debian developer, member of kernel, installer and LTS teams
Thank you!
Nathaniel, I'll keep this bug open till possibly the perf events will
become available for normal users. Till then I require you to use the
workaround above if you feel like it.
Cheers,
Tomasz
