Re: Re: perf tracepoints for regular user?

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Jan 20, 2016 at 12:50:33PM +0100, Benjamin King escreveu:
> Hi Arnaldo,
> 
> > > $ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
> > > mount: can't find /sys/kernel/debug/tracing in /etc/fstab
> > > $ mount|grep debug
> > > none on /sys/kernel/debug type debugfs (rw,mode=755,mode=755)
> > 
> > Ok, your kernel is old and doesn't have the tracefs:

Not having tracefs, if that is indeed the case, only means that the
remount isn't needed, as what is in tracefs is what, before its
existence, lived in a debugfs directory, /sys/kernel/debug/tracing, i.e.
remounting just /sys/kernel/debug/ would then be enough.

> > [acme@zoo ~]$ mount | egrep \(debug\|trace\)fs
> > debugfs on /sys/kernel/debug type debugfs (rw,relatime,seclabel,mode=755)
> > tracefs on /sys/kernel/debug/tracing type tracefs (rw,relatime,mode=755)
> > [...]
> > [acme@zoo ~]$ uname -r
> > 4.3.0+
 
> That's odd. According to kernelnewbies.org (Yes, I am that much of a
> kernel hacker :-) ), tracefs should be in since 4.1 and I'm on 4.2,
> but I can only find CONFIG_DEBUG_FS in my kernel configuration. There
> is no mentioning of a corresponding CONFIG_TRACE_FS there.
 
> I'll try to upgrade to a more recent kernel and stop bugging you guys until then.