Sync throttle flags

[Gingeropolous]

Sorry if I beat you to posting this @fluffypony , but I wanted to expand on the idea.

New Feature - Initial Synchronization (or heavy synch) throttling flag with different levels, or just a general throttling flag.

Goal - gets at decreasing the Cost of Node metric.

Rambling thoughts:

in general, perhaps the "throttle while syncing" should be a flag with different levels. I just had a VPS provider shutdown my service because the initial sync was gobbling the CPU too much and who knows how many other resources. Yeah, I know, this could be addressed with "nice" or whatever, but having it built in might make it function better? I dunno. The bastards could've charged me 15 bucks just to release the server from its banished state. Luckily, they were nice.

So, if a 5 point scale,

0 = no throttle
1 = limit number of incoming connections that can use you to sync during initial sync (default)
2 = no incoming connections during initial sync
3 = no incoming connections keep CPU below 75%
4 = no inc and keep CPU < 50%

Now I have five points.

[moneromooo-monero]

You have 6 points.

[Gingeropolous]

Now I have 5 points.

[moneromooo-monero]

I can't argue with that.

[ghost]

Perhaps your node could run a local function such as 'time to validate x signatures' or 'time to fetch x bytes from peers' and use these as internal metrics against which to drive the CPU usage whilst keeping the initial sync time as low as possible?

[ghost]

Local *calibration function

[dEBRUYNE-1]

+proposal