Can interprocess communication be as fast as in-process events (using wcf and c#)

Question

I have an application that performs analysis on incoming event flow (CEP engine). This flow can come from different sources (database, network, etc...).

For efficient decoupling, I want this service to expose a named pipe using wcf, and allow a different application to read the data from the source and feed it into the service.

So, one process is in charge of getting and handling the incoming data while the other for analyzing it, connecting the two using wcf with named pipes binding. They both will be deployed on the same machine.

Question is, will I notice a lower throughput using wcf in the middle then if I would have simply coupled the two services into a single process and use regular events?

Answer 1

No, in modern mainstream operating systems, IPC will never be, can never be, as fast as in-process eventing. The reason for this is the overhead of context switching associated to activating different processes. Even for a multi-core system where distinct processes run on distinct cores, though they each run independently (and therefore there is no cost associated to activating one process versus another - they are both always active), the communication across processes still requires crossing security boundaries, hitting the network stack (even if using pipes), and so on. Where a local function call will be on the order of 1000's of cpu cycles to invoke, an IPC will be millions.

So IPC will be slower than in-process communication. Whether that actually matters in your case, is a different question. For example, suppose you have an operation that requires Monte Carlo simnulation that runs for 2 hours. In this case it really doesn't matter whether it takes 1ms or 1000ms in order to invoke the operation.

Usually, performance of the communication is not what you want to optimize for. Even if performance is important, focusing on one small aspect of performance - let's say, whether to use IPC or local function calls - is probably the wrong way to go about things.

I assumed "CEP" referred to "complex event processing" which implies high throughput, high volume processing. So I understand that performance is important to you.

But, for true scalability and reliability, you cannot simply optimize in-process eventing; You will need to rely on multiple computers and scale out. This will imply some degree of IPC, one way or the other. It's obviously important to be efficient at the smaller scale (events) but your overall top-end performance will be largely bounded by the architecture you choose for scale out.

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WCF is nice because of the flexibility it allows in moving building blocks from the local machine to a remote machine, and because of the Channel stack, you can add communication services in a modular way.

Whether this is important to you, is up to you to decide.