[PATCH v8 1/2] perf, uncore: Adding documentation for ThunderX2 pmu uncore driver

[Kulkarni, Ganapatrao]

The SoC has PMU support in its L3 cache controller (L3C) and in the
DDR4 Memory Controller (DMC).

Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@xxxxxxxxxx>
---
 Documentation/perf/thunderx2-pmu.txt | 106 +++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 Documentation/perf/thunderx2-pmu.txt

diff --git a/Documentation/perf/thunderx2-pmu.txt b/Documentation/perf/thunderx2-pmu.txt
new file mode 100644
index 000000000000..9f5dd7459e68
--- /dev/null
+++ b/Documentation/perf/thunderx2-pmu.txt
@@ -0,0 +1,106 @@
+
+Cavium ThunderX2 SoC Performance Monitoring Unit (PMU UNCORE)
+==========================================================================
+
+ThunderX2 SoC PMU consists of independent system wide per Socket PMUs such
+as Level 3 Cache(L3C) and DDR4 Memory Controller(DMC).
+
+DMC has 8 interleave channels and L3C has 16 interleave tiles. Events are
+sampled for default channel(i.e channel 0) and prorated to total number of
+channels/tiles.
+
+DMC and L3C, Each PMU supports up to 4 counters. Counters are independently
+programmable and can be started and stopped individually. Each counter can
+be set to sample specific perf events. Counters are 32 bit and do not support
+overflow interrupt; they are sampled at every 2 seconds.
+
+PMU UNCORE (perf) driver:
+
+The thunderx2-pmu driver registers several perf PMUs for DMC and L3C devices.
+Each of the PMUs provides description of its available events
+and configuration options in sysfs.
+	see /sys/devices/uncore_<l3c_S/dmc_S/>
+
+S is socket id.
+Each PMU can be used to sample up to 4 events simultaneously.
+
+The "format" directory describes format of the config (event ID).
+The "events" directory provides configuration templates for all
+supported event types that can be used with perf tool.
+
+For example, "uncore_dmc_0/cnt_cycles/" is an
+equivalent of "uncore_dmc_0/config=0x1/".
+
+Each perf driver also provides a "cpumask" sysfs attribute, which contains a
+single CPU ID of the processor which is likely to be used to handle all the
+PMU events. It will be the first online CPU from the NUMA node of the PMU device.
+
+Example for perf tool use:
+
+perf stat -a -e uncore_dmc_0/cnt_cycles/ sleep 1
+
+perf stat -a -e \
+uncore_dmc_0/cnt_cycles/,\
+uncore_dmc_0/data_transfers/,\
+uncore_dmc_0/read_txns/,\
+uncore_dmc_0/write_txns/ sleep 1
+
+perf stat -a -e \
+uncore_l3c_0/read_request/,\
+uncore_l3c_0/read_hit/,\
+uncore_l3c_0/inv_request/,\
+uncore_l3c_0/inv_hit/ sleep 1
+
+The driver does not support sampling, therefore "perf record" will
+not work. Per-task (without "-a") perf sessions are not supported.
+
+L3C events:
+============
+
+read_request:
+	Number of Read requests received by the L3 Cache.
+	This include Read as well as Read Exclusives.
+
+read_hit:
+	Number of Read requests received by the L3 cache that were hit
+	in the L3 (Data provided form the L3)
+
+writeback_request:
+	Number of Write Backs received by the L3 Cache. These are basically
+	the L2 Evicts and writes from the PCIe Write Cache.
+
+inv_nwrite_request:
+	This is the Number of Invalidate and Write received by the L3 Cache.
+	Also Writes from IO that did not go through the PCIe Write Cache.
+
+inv_nwrite_hit
+	This is the Number of Invalidate and Write received by the L3 Cache
+	That were a hit in the L3 Cache.
+
+inv_request:
+	Number of Invalidate request received by the L3 Cache.
+
+inv_hit:
+	Number of Invalidate request received by the L3 Cache that were a
+	hit in L3.
+
+evict_request:
+	Number of Evicts that the L3 generated.
+
+NOTE:
+1. Granularity of all these events counter value is cache line length(64 Bytes).
+2. L3C cache Hit Ratio = (read_hit + inv_nwrite_hit + inv_hit) / (read_request + inv_nwrite_request + inv_request)
+
+DMC events:
+============
+cnt_cycles:
+	Count cycles (Clocks at the DMC clock rate)
+
+write_txns:
+	Number of 64 Bytes write transactions received by the DMC(s)
+
+read_txns:
+	Number of 64 Bytes Read transactions received by the DMC(s)
+
+data_transfers:
+	Number of 64 Bytes data transferred to or from DRAM.
-- 
2.18.0