Introduction: Intel PMWatch is a tool that monitors and reports the behavior of the Intel® Optane™ DC persistent memory.
It consists of a data collector.

Pre-requisites:
Linux OS - Fedora or RHEL with nvdimm driver support
Intel® Optane™ DC persistent memory firmware version: 01.01.00.5142 and newer

PMWatch instructions:
Run "source pmw_vars.sh" to set up the environment before using the tool.

Tools Usage:
pmwatch "<sampling interval>" "<number of samples>" -f outputfile.csv

Example: "pmwatch 1 100" reads the counters every 1 second 100 times.

The output of PMWatch is in a CSV format listing the metrics for each DIMM on the system and outputs the counts for each interval.

Explanation of metrics:

Memory performance metrics:
bytes_read (derived)   : number of bytes transacted by the read operations
bytes_written (derived): number of bytes transacted by the write operations
Note: The total number of bytes transacted in any sample is computed as bytes_read (derived) + 2 * bytes_written (derived).

Formula:
bytes_read   : (read_64B_ops_received - write_64B_ops_received) * 64
bytes_written: write_64B_ops_received * 64


read_hit_ratio (derived) : measures the efficiency of the buffer in the read path. Range of 0.0 - 0.75.
write_hit_ratio (derived): measures the efficiency of the buffer in the write path. Range of 0.0 - 0.1.

0.75   : indicates 100% sequential write traffic
> 0.75 : indicates writing to 64B addresses that are still in the write buffer (never had to go to media)
1 or ~1: likely writing to a specific address or small range of addresses (fitting in write buffer) for long periods of time.

Formula:
read_hit_ratio : (cpu_read_ops - media_read_ops) / cpu_read_ops
write_hit_ratio: (cpu_write_ops - media_write_ops) / cpu_write_ops


media_read_ops (derived) :
media_write_ops (derived):
Number of read and write operations performed to the physical media. Each operation transacts a 256 bytes operation.

Formula:
media_read_ops : (read_64B_ops_received - write_64B_ops_received) / 4
media_write_ops: write_64B_ops_received / 4


read_64B_ops_received :
write_64B_ops_received:
Number of read and write operations performed from/to the physical media. Each operation transacts a 64byte operation. These operations includes commands transacted for maintenance as well as the commands transacted by the CPU.


cpu_read_ops :
cpu_write_ops:
Number of read and write operations received from the CPU (memory controller), for the Memory Mode and AppDirect Mode partitions.

Health Information:
health_status:
Overall health summary.

Value: Health Status
0: Normal
1: Non-critical
2: Critical
3: Fatal

lifespan_used:
The module’s used life as a percentage value of factory expected like span.

lifespan_remaining:
The module’s remaining life as a percentage value of factory expected like span.

power_on_time:
The lifetime the DIMM has been powered on in seconds.

uptime:
The current uptime of the DIMM for the current power cycle in seconds.

last_shutdown_time:
The time the system was last shutdown. The time is represented in epoch (seconds).

media_temp :
The media’s current temperature in degrees Celsius.

controller_temp :
The controller’s current temperature in degrees Celsius.

max_media_temp :
The media’s the highest temperature reported in degrees Celsius.

max_controller_temp :
The controller’s highest temperature reported in degrees Celsius.