Re: [PATCH 1/3] perf auxtrace: Support for perf report -D for s390

From: Arnaldo Carvalho de Melo
Date: Fri Aug 03 2018 - 09:33:05 EST

Em Fri, Aug 03, 2018 at 12:07:58PM +0200, Hendrik Brueckner escreveu:
> Arnaldo,
> On Thu, Aug 02, 2018 at 09:49:09AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Aug 02, 2018 at 09:46:20AM +0200, Thomas Richter escreveu:
> > > Add initial support for s390 auxiliary traces using the
> > > CPU-Measurement Sampling Facility.
> >
> > Could you please provide one or two paragraphs explaining what is this
> > "CPU-Measurement Sampling Facility", in which hardware this is available
> > (all s/390 hardware has it? Just the 64-bit model(s)?) and provide a
> > public URL for people interested in further reading?
> The CPU-Measurement Facility (CPU-MF) provides a set of functions to obtain
> performance information on the mainframe. Basically, it was introduced
> with System z10 years ago for the z/Architecture, that means, 64-bit.
> For Linux, there are two facilities of interest, counter facility and sampling
> facility. The counter facility provides hardware counters for instructions,
> cycles, crypto-activities, and many more.
> The sampling facility is a hardware sampler that when started will write
> samples at a particular interval into a sampling buffer. At some point,
> for example, if a sample block is full, it generates an interrupt to collect
> samples (while the sampler continues to run).
> Few years ago, I started to provide the a perf PMU to use the counter
> and sampling facilities. Recently, the device driver was updated to also
> "export" the sampling buffer into the AUX area. Thomas now completed the
> related perf work to interpret and process these AUX data.
> If people are more interested in the sampling facility, they can have a
> look into:
> - The Load-Program-Parameter and the CPU-Measurement Facilities, SA23-2260-05
> and to learn how-to use it for Linux on Z, have look at chapter 54,
> "Using the CPU-measurement facilities" in the:
> - Device Drivers, Features, and Commands, SC33-8411-34


Thanks a lot, I added this to the first commit, people investigating
this should be able to find that when doing research about the
implementation details.

- Arnaldo