Re: [PATCH] S/390: User space support for hardware sampling

[Andreas K. <kr...@li...>]

Hi Maynard,

here is an updated version of the patch. As you suggested I'm now using a pseudo counter
with two separate events.  The user can then disable/enable hwsampling by picking the
proper event.

I also tried to get away without adding S/390 specific options to opcontrol but ...

* Use buffer-size also for the buffer size within the hardware sampling module. Actually
it might makes sense to be able to specify both values separately. While buffer size
specifies the number of samples which should fit into the oprofile kernel buffer the
buffer size for the hardware sampling is given in number of 2MB areas allocated for the
hardware sampling facility. However these values in the end will also pass through the
oprofile kernel buffer so the buffer-size option still has a meaning in that case and to
my opinion should not be overriden.

* Use the count value for the samping rate.  This values is multiplied with the callgraph
depth what for a sampling rate doesn't make sense. Also I would not be able to give the
user a proper error message in case the value does not fit into the range as specified by
the hardware facility.

So for now I still have two s390 specific options which need to be added to opcontrol.
However thanks to the event interface the patch is much simpler now.

Bye,

-Andreas-