RE: [PATCH] perf: imx8_ddr_perf: calculate ddr bandwidth via virtual event read-bytes/write-bytes

[Joakim Zhang <qiangqing.zhang@nxp.com>]

> -----Original Message-----
> From: Will Deacon <will@kernel.org>
> Sent: 2019年7月9日 23:56
> To: Joakim Zhang <qiangqing.zhang@nxp.com>
> Cc: mark.rutland@arm.com; Frank Li <frank.li@nxp.com>;
> kernel@pengutronix.de; dl-linux-imx <linux-imx@nxp.com>;
> linux-arm-kernel@lists.infradead.org
> Subject: Re: [PATCH] perf: imx8_ddr_perf: calculate ddr bandwidth via virtual
> event read-bytes/write-bytes
> 
> On Tue, Jul 09, 2019 at 05:46:44AM +0000, Joakim Zhang wrote:
> > We can calculate ddr bandwidth via virtual event
> > read-bytes/write-bytes based on ddr burst width, which actually share
> > event read-cycles/write-cycles. Burst width is 32 bit on i.MX8 board.
> >
> > The ddr interface will generate 2 up edges and 2 down edges in an
> > internal clock cycle, so it can pass 4 beats of data. 4 bytes of each
> > beat if ddr burst width is 32 bit.
> >
> > for example:
> > perf stat -a -e imx8_ddr0/read-bytes/,imx8_ddr0/write-bytes/ ls
> 
> I don't think you should be doing this in the kernel. Can you look at
> implementing it in perf tool instead by adding a .json file for your PMU and
> expressing this compound event using "MetricExpr"?

Hi Will,

I try to implement it in perf tool, but it shows nothing with perf list metricgroup.

A. Add JSON metric.
diff --git a/tools/perf/pmu-events/arch/arm64/imx/imx8/ddr-metric.json b/tools/perf/pmu-events/arch/arm64/imx/imx8/ddr-metric.json
new file mode 100644
index 000000000000..3588dc5a4f46
--- /dev/null
+++ b/tools/perf/pmu-events/arch/arm64/imx/imx8/ddr-metric.json
@@ -0,0 +1,20 @@
+[
+    {
+       "PublicDescription": "Calculate DDR read bandwidth based on read-cycles event. DDR interface generates 2 up and 2 down edges in an internal clock cycle, can pass 4 beats of data. 4 bytes of each beat if DDR burst width is 32 bit.",
+       "MetricName": "imx8_ddr0/read-bytes/",
+       "MetricGroup": "bandwidth",
+       "MetricExpr": "imx8_ddr0/read-cycles/ * 4 * 4",
+        "Unit": "MB",
+       "ScaleUnit": "0.000001",
+       "BriefDescription": "DDR read bandwidth"
+    },
+    {
+       "PublicDescription": "Calculate DDR write bandwidth based on write-cycles event. DDR interface generates 2 up and 2 down edges in an internal clock cycle, can pass 4 beats of data. 4 bytes of each beat if DDR burst width is 32 bit.",
+       "MetricName": "imx8_ddr0/write-bytes/",
+       "MetricGroup": "bandwidth",
+       "MetricExpr": "imx8_ddr0/write-cycles * 4 * 4",
+        "Unit": "MB",
+       "ScaleUnit": "0.000001",
+       "BriefDescription": "DDR write bandwidth"
+    }
+]
diff --git a/tools/perf/pmu-events/arch/arm64/mapfile.csv b/tools/perf/pmu-events/arch/arm64/mapfile.csv
index 927fcddcb4aa..12d378dca0d1 100644
--- a/tools/perf/pmu-events/arch/arm64/mapfile.csv
+++ b/tools/perf/pmu-events/arch/arm64/mapfile.csv
@@ -20,3 +20,4 @@
 0x00000000430f0af0,v1,cavium/thunderx2,core
 0x00000000480fd010,v1,hisilicon/hip08,core
 0x00000000500f0000,v1,ampere/emag,core
+0x000000004108d040,v1,imx/imx8,core

B. Test
root@imx8qxpmek:~# perf list metricgroup

List of pre-defined events (to be used in -e):

root@imx8qxpmek:~#

It generates the C source file, 'pmu-events.c', as /tools/perf/pmu-events/README said, but it can't generate this C file on my side.

Please tell me if something I missed. Thanks a lot!

Best Regards,
Joakim Zhang
> Will
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