Thursday September 15, 2005

Dataspace Profiling Knowledge – Look Inside the Machine!

With Insight and Experience, Knowledge drives Change. For peak productivity, you need Action through Knowledge.

Let’s Look Inside the Machine!

For Dataspace Profiling, this table expresses the Machine, application and hardware:

The first row shows the Software View and the Hardware View groupings of various Categories of Machine Resources: Software Execution, Program Source, Virtual Memory allocated by the Software, Physical Memory of the Hardware caching portions of the Virtual Memory, the Cache Hierarchy caching portions of the Physical Memory, the Execution Units, and Time.

Stacked Cells in Columns represent nested Collections of Structures. For example, Load Objects comprise Functions that comprise Instructions. Similarly, Processor Boards comprise Processors that comprise Cores that comprise Strands.

The Cache Hierarchy contains the MMU that contains TLB Translation Entries that map a Virtual Page to a Physical Page. The External Cache comprises External Cache Lines that may contain External Cache Sub-Blocks. The Level One Cache comprises Level One Cache Lines. To simplify this explanation, assume that the machine has only one size for every one of the Cache Hierarchy Components; however, Dataspace Profiling handles an arbitrary number of sizes.

Each Color shows an association among Categories of Machine Resources. For example, A TLB Entry will map Virtual Memory Pages to Physical Memory Pages. Dataspace Profiling manages this association for you with the Object Definitions. When a cost occurs in filling the TLB Entry, Dataspace Profiling automatically manages which Virtual Memory Page and which Physical Memory Page was affected.

The Colors let you gain Insight from one Machine Category to another. Filter on one Category, and change Perspective to the corresponding Category of the same Color. Filtering among Categories enables you narrow down a bottleneck.

In my example, one Category is the Program View of Memory (Virtual Page), another is the Hardware View of Memory (Physical Page), and the third is the Hardware View for the Cache Hierarchy, the TLB Entry. List the Virtual Pages using this TLB Entry? (Filter by TLB Entry, view by Virtual Pages.) Which Physical Page is mapped by this Virtual Page? (AND Filter by the Virtual Page, view by Physical Page).

For another example, observe your Application from the Perspective of Processor Boards. For the Processor Board using the most time, which Memory Boards does this Processor Board use? Note the Colors above, we can find out by filtering on the Processor Board; and changing Perspective to the Memory Boards. Dataspace Profiling provides you the answer!

You can continue to gain Knowledge about your Application by repeating this process, drilling deeper. By Filtering by a Memory Board AND a Processor Board, you gain Knowledge of which other objects in the machine are using both.

For example, repeated AND Filtering allows powerful observations. From which Threads inside which Processes running on what Processors, using which Type Definitions and which Virtual Memory Addresses that were placed on which remote Memory Board, and at what Time during the Application execution.

In my previous blog entry, I walked you through a series of Insights gained through Dataspace Profiling Technology. Now you gain the Knowledge whether the Virtual Addresses are heavily shared (many Processes with one Virtual Memory per Physical Memory or Cache Structure), or they are falsely shared and we have a conflict (many Virtual Memories to one Physical Memory; or many Physical Memories to one Cache Structure). We know which Virtual Addresses, Virtual Pages, Processes, Threads, User-Defined Structures, Functions are affected. You now have the Knowledge. You can Act through Knowledge.

Dataspace Profiling – Look Inside the Machine!