Extended Events PerfObject Events

SQL Server 2008 R2 Service Pack 1 provides a new set of Events in Extended Events to collect performance counter data from the Windows OS that would be really useful to monitoring SQL Server. The first place I can find that they were mentioned is on a blog post by Mark Weber, a PFE for SQL and SAP at Microsoft. However, a few weeks ago a question was asked about these counters one of the forums and the question was around how to use them. I looked at the Events and found out that they aren’t really useable in their current implementation, something that is disappointing since being able to collect the data provided by these Events would really benefit most DBA’s out there.

If you look at the Events and columns, these events collect information about the Logical Disk, Processor, Process for the SQL instance, and System at 15 second intervals and makes the data available through Extended Events.

SELECT name, description
FROM  sys.dm_xe_objects
WHERE name like 'perfobject_%'

name	description
perfobject_process	Returns a set of counters associated with the Process performance object. The event occurs once every 15 seconds for both the SQL Server and SQL Agent processes.
perfobject_system	Returns a set of counters associated with the System performance object. The event occurs once every 15 seconds.
perfobject_logicaldisk	Returns a set of counters associated with the Logical Disk performance object. The event occurs once every 15 seconds for each hard or fixed disk drive.
perfobject_processor	Returns a set of counters associated with the Processor performance object. The event occurs once every 15 seconds for each processor in the system.

If we look at the columns, we’ll see that the columns actually represent the individual counters under the categories exposed by the Event names. For example, the perfobject_logicaldisk event returns the following columns:

SELECT
    object_name, 
    name AS column_name, 
    description
FROM  sys.dm_xe_object_columns
WHERE object_name = 'perfobject_logicaldisk'
  AND column_type = 'data'
ORDER BY object_name, name

object_name	column_name	description
perfobject_logicaldisk	average_disk_bytes_per_read	Shows the average number of bytes transferred from the disk during read operations.
perfobject_logicaldisk	average_disk_bytes_per_transfer	Shows the average number of bytes transferred to or from the disk during write or read operations.
perfobject_logicaldisk	average_disk_bytes_per_write	Shows the average number of bytes transferred to the disk during write operations.
perfobject_logicaldisk	average_disk_queue_length	Shows the average number of both read and write requests that were queued for the selected disk during the sample interval.
perfobject_logicaldisk	average_disk_read_queue_length	Shows the average number of read requests that were queued for the selected disk during the sample interval.
perfobject_logicaldisk	average_disk_seconds_per_read	Shows the average time, in seconds, of a read operation from the disk.
perfobject_logicaldisk	average_disk_seconds_per_transfer	Shows the time, in seconds, of the average disk transfer.
perfobject_logicaldisk	average_disk_seconds_per_write	Shows the average time, in seconds, of a write operation to the disk.
perfobject_logicaldisk	average_disk_write_queue_length	Shows the average number of write requests that were queued for the selected disk during the sample interval.
perfobject_logicaldisk	current_disk_queue_length	Shows the number of requests outstanding on the disk at the time that the performance data is collected.
perfobject_logicaldisk	disk_bytes_per_second	Shows the rate at which bytes are transferred to or from the disk during write or read operations.
perfobject_logicaldisk	disk_read_bytes_per_second	Shows the rate at which bytes are transferred from the disk during read operations.
perfobject_logicaldisk	disk_reads_per_second	Shows the rate at which read operations are performed on the disk.
perfobject_logicaldisk	disk_transfers_per_second	Shows the rate at which read and write operations are performed on the disk.
perfobject_logicaldisk	disk_write_bytes_per_second	Shows the rate at which bytes are transferred to the disk during write operations.
perfobject_logicaldisk	disk_writes_per_second	Shows the rate at which write operations are performed on the disk.
perfobject_logicaldisk	free_megabytes	Shows the unallocated space, in megabytes, on the disk drive. One megabyte is equal to 1,048,576 bytes.
perfobject_logicaldisk	instance_name	The logical disk drive name
perfobject_logicaldisk	percent_disk_read_time	Shows the percentage of time that the selected disk drive is busy servicing read or write requests.
perfobject_logicaldisk	percent_disk_time	Shows the percentage of time that the selected disk drive is busy servicing read requests.
perfobject_logicaldisk	percent_disk_write_time	Shows the percentage of time that the selected disk drive is busy servicing write requests.
perfobject_logicaldisk	percent_free_space	Shows the percentage of the total usable space on the selected logical disk drive that is free.
perfobject_logicaldisk	percent_idle_time	The percentage of time during the sample interval that the disk was idle.
perfobject_logicaldisk	split_io_per_second	The rate at which I/Os to the disk were split into multiple I/Os.

This all seems good, until we actually use the Events in an Event Session and take a look at the data being returned.

CREATE EVENT SESSION [XE_PerfCounters] 
ON SERVER 
ADD EVENT sqlserver.perfobject_logicaldisk 
ADD TARGET package0.ring_buffer;
GO

Unfortunately, the counters are returning Raw values for the Event and the necessary Base counters that are required to give these values any useful meaning have been left out of the Events data. Looking at this in my test environment, it appears the counter values pulled for the perfobject_ Events are pulled directly from Win32_PerfRawData_PerfDisk_LogicalDisk, but if you look at the CookingType requirements for the counters in Win32_PerfFormattedData_PerfDisk_LogicalDisk the raw values have to be calculated by their base values for them to have meaning: