What did you expect ?

One of these days Peter Rodgers is bound to mention in the NetKernel Newsletter that I repeat/rehash a lot of what he and Tony have been saying all along. Of course I do. What did you expect ?

I want to focus on that question today. For in these days of multi-core systemscheap memory (buy lots) even cheaper storage (buy lots lots) and unlimited bandwidth that question is often not even thought of until an application is going through the final performance tests.

And at that point your company's performance guy (been there, done that) might say - bad - things like :
- Those response times are - imo - not acceptable for production, what did you expect ?
- That is a very high throughput you've got there, what did you expect ?
- The cpus on the system are going red-hot, what did you expect ?

With a deadline looming like the sword of Damocles above your head, these are not things you want to hear.

The question "What do you expect ?" should be asked a lot earlier, it should be asked in the design phase, before any coding is done. The cost of overhauling a design is a lot lower than the cost of overhauling a completely finished application.

Now, next to the fact that NetKernel has an extremely light footprint on your systems as well as superior caching, it also has the tools to help you stay within the limits of what you expect.

Take nkperf. You can install this tool from the repository and it tells you how your system behaves. Not relevant you say ? Read this newsletter entry again. Or if you'd rather not have a rehashed ;-) story, look at what I found this morning on my own laptop (Windows, dual core intel) :

Oops, there is something very fishy with my caching performance. Especially when you look at this :

The second graph is from a virtual machine (CentOS, single core), running on the same laptop !

So why is the blue line flat on the first graph ? I don't know, but I better find out before I make any conclusions about applications running on that system. And that is the point of my story. You must know what you expect, what the constraints on your application are before you write it. And NetKernel can help you with that.

Footnote :
On seeing the above issue, the 1060 Research crew jumped in and pointed out the obvious cause of the flatliner. I've got a pretty speedy laptop. And to optimize caching, NetKernel has
 a cost threshold parameter described as : cost of an item must be at least this high before eligible for caching. Can you see where this is going ? The native machine (but not the vm) responded so fast that nothing was costly enough to be cached. Hence the flatliner.

Easily ammended, I set the cost threshold to 0. And look