Re: [PATCH 1/2]: S/390: Add event interface to the System z hardware sampling kernel part

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

On 11/16/2011 10:41 PM, Robert Richter wrote:
> Can't we drop /dev/oprofile/hwsampling/ and only support it with
> "timer" forced by a kernel parameter to be backward compatible with
> older oprofile daemons? Would make live easier.

No. The /dev/oprofile/hwsampling file system is needed also with the new interface.  The
user space tools need the /dev/oprofile/hwsampling/hw_min|max_interval values in order to
do proper parameter checking. These values can only be provided by the kernel module.

> If possible I would rather prefer to not have it at all, but if the
> daemon requires it anyway we should at least only allow certain values
> to be used. The kernel should check this. In the end this would be
> only unit_mask and extra which should be set to 0 or so. A check is
> required also for kernel and user flags, so it shouldn't be a big
> deal to implement this for all.

Ok done. I've also removed the `extra' file. This does not seem to be needed.

> Usually we take <arch>/<model> where <arch> is as uname reports it,
> but this is not always consistent. Doing so it would be
> "s390/systemz", but not sure if this would fit here.

This would be "s390x/z10" then. Unfortunately the availability does not only depend on the
CPU level. It also depends on the millicode-level and the machine configuration. The
feature also is the same way available on the z196 and this probably stays like this for a
while.

Bye,

-Andreas-