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Date:   Fri, 3 Aug 2018 10:32:52 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Hendrik Brueckner <brueckner@linux.ibm.com>
Cc:     Thomas Richter <tmricht@linux.ibm.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com
Subject: Re: [PATCH 1/3] perf auxtrace: Support for perf report -D for s390
Message-ID: <20180803133252.GE7996@kernel.org>
References: <20180802074622.13641-1-tmricht@linux.ibm.com>
 <20180802074622.13641-2-tmricht@linux.ibm.com>
 <20180802124909.GB7996@kernel.org>
 <20180803100758.GA28475@linux.ibm.com>
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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
>   http://www-01.ibm.com/support/docview.wss?uid=isg26fcd1cc32246f4c8852574ce0044734a
> 
> 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
>   http://public.dhe.ibm.com/software/dw/linux390/docu/l416dd34.pdf

-----------------------

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