Not only is the answer, yes (it's a throughput-delay plot or XR plot in my notation), but that particular plot comes from my GCaP course notes. There, I use it to analyze the comparative performance of a functional multiprocessor (NS6000) and a symmetric multiprocessor (SC2000). Note how the two curves cross at around 1500 OPS. You can ask yourself why and if you can't come up with an explanation, you should be registering for a Guerrilla class. :)
The above XR plot also serves as a useful reminder that the throughput and response-time metrics are not only dependent on one another, but they are generally dependent in a nonlinear way—despite what some experts may claim:What is truly alarming, however, is that I am unable to find this example in any of my books; after a quick and non-exhaustive search. I would have expected it was discussed in The Practical Performance Analyst (since the example is of that vintage), but I don't see it. If you happen to spot it or know which book chapter it is in, please let me know.
Mon, 16 Sep 2002 08:04:04 +1000
...in reality, Latency & Throughput are two completely different metrics associated with performance. Latency isn't related to Throughput and vice-versa. ...
Since the throughput-delay product is merely a statement of Little's law, N = X*R, you can use it to trivially calculate the number of thingies (N) at any point on the XR plot. Then, you can plot say, throughput as a function of N, i.e., X = X(N), which you weren't given in the original visual representation. For the above example, N is the number of client generators impressing load on the test rig:
Now you can see clearly that the SC2000 throughput has reached a saturation value of about 2500 OPS by 100 generators. So, there would be no virtue in driving the NFS system with more load generators (even if there is NIC bandwidth available) because the response time will be begin to climb embarrassingly.
Although the above example is dated in terms of the technology, it is timeless in terms of its instruction. With that in mind, you can review more modern XR plots on the SPEC.org website where the current NFS benchmark is called SFS2008. Here are some SPEC throughput-delay plots from 2011:
Cautionary note: Be careful to distinguish between the (band)width of the network pipe, i.e., Xmax, vs. the number of packets per second, i.e., X, being pushed through that pipe.
- "determines the amount of data that can be in transit in the network"
- [is a] "very important concept in a window-based protocol such as TCP, as throughput is bound by" [it]
- can be conveniently calculated for TCP packets