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From: Leo Yan <leo.yan@linaro.org>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: mathieu.poirier@linaro.org, corbet@lwn.net,
	alexander.shishkin@linux.intel.com, coresight@lists.linaro.org,
	acme@kernel.org, peterz@infradead.org, mingo@redhat.com,
	Mike.leach@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 5/5] docs: coresight: Document snapshot mode
Date: Mon, 13 May 2019 19:16:15 +0800	[thread overview]
Message-ID: <20190513111615.GA32010@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <77e437ed-99b2-670e-7e29-33be584f2bd0@arm.com>

Hi Suzuki,

On Mon, May 13, 2019 at 09:37:01AM +0100, Suzuki K Poulose wrote:
> Hi,
> 
> On 11/05/2019 08:32, Leo Yan wrote:
> > On Wed, May 01, 2019 at 11:50:52AM -0600, Mathieu Poirier wrote:
> > 
> > [...]
> > 
> > > +2.2) Snapshot mode:
> > > +
> > > +Using perf's built-in snapshot mode with CoreSight tracers is supported - to
> > > +do so the '-S' command line option needs to be specified.  Since current sink
> > > +devices are used in double-buffer mode when operated from the perf interface,
> > > +the size of the perf ring buffer needs to be adjusted to match the size of the
> > > +buffer used by the CoreSight sinks.  From the perf command line it is possible
> > > +to specify the number of pages to use for a session using the '-m,X' option,
> > > +where X is the amount of pages.
> > > +
> > > +The system memory buffer used by ETR devices is automatically adjusted
> > > +to match the size of the perf ring buffer and as such does not need to be
> > > +modified on the perf command line.  For ETB and ETF devices the perf ring
> > > +buffer size need to be adjusted to match the size of the internal buffer.
> > > +
> > > +The following examples assume a system page size of 4096 byte:
> > > +
> > > +	# cat /sys/bus/coresight/devices/20010000.etb/mgmt/rdp
> > > +	0x2000
> > > +	# perf record -e cs_etm/@20010000.etf/ -S -m,8 --per-thread $APP
> > 
> > In this case it shows the usage for etb, thus should:
> > s/20010000.etf/20010000.etb/
> > 
> > BTW, the user needs to convert the rdp to byte size with multiplying 4,
> > it's good to explain for this in the doc or give related info in the
> > driver warning log.
> 
> If at all we want to match the aux space size with that of the device buffer,
> I recommend exposing this via a new "buf_pages" attribute under the sysfs to
> help the user.

Agree, I also saw you suggested in another email.  Using "buf_pages"
is directive and consistent for different sink devices.

Thanks,
Leo Yan

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  reply	other threads:[~2019-05-13 11:23 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01 17:50 [PATCH 0/5] coresight: Fix snapshot mode Mathieu Poirier
2019-05-01 17:50 ` [PATCH 1/5] coresight: Fix buffer size in " Mathieu Poirier
2019-05-07  7:38   ` Leo Yan
2019-05-07 17:24     ` Mathieu Poirier
2019-05-07  8:50   ` Suzuki K Poulose
2019-05-07 20:22     ` Mathieu Poirier
2019-05-01 17:50 ` [PATCH 2/5] coresight: tmc-etf: Fix snapshot mode update function Mathieu Poirier
2019-05-07  8:13   ` Leo Yan
2019-05-07 17:16     ` Mathieu Poirier
2019-05-07  9:22   ` Suzuki K Poulose
2019-05-01 17:50 ` [PATCH 3/5] coresight: perf: Don't set the truncated flag in snapshot mode Mathieu Poirier
2019-05-07  8:29   ` Leo Yan
2019-05-07 17:44     ` Mathieu Poirier
2019-05-01 17:50 ` [PATCH 4/5] perf tools: Properly set the value of 'old' " Mathieu Poirier
2019-05-07  8:44   ` Leo Yan
2019-05-07 17:59     ` Mathieu Poirier
2019-05-01 17:50 ` [PATCH 5/5] docs: coresight: Document " Mathieu Poirier
2019-05-11  7:32   ` Leo Yan
2019-05-13  8:37     ` Suzuki K Poulose
2019-05-13 11:16       ` Leo Yan [this message]
2019-05-13 20:01         ` Mathieu Poirier
2019-05-13 20:12           ` Mathieu Poirier

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