Geth 6.2: miner.start() returns null and miner's hash-rate drop for all miners down due to the update

Question

On Geth Version: 1.6.2-unstable miner.start() returns null, it used to return number of processes assigned. Is it normal? miner.start(num) num identifies the thread number?

> miner.stop()
true
> miner.start(4)
null

I have a small private net and there is only one miner. The miner used to work for almost couple of months with 503.7 KH/s (since it has been launched with geth v5.9) but now it works with 103.7 KH/s when I updated geth with 6.2 there is this sudden drop down. This drop down affected all the miner's hash rate and I observe that all's hash-rate is drop down around 5 times.

This change occur for my other nodes where hash-rate is get dramatically slower. When I check top geth consumes all the CPU power, I assume miner works with full CPU power.

[Q] What might be the reason for miner's hash rate drop down (almost 5 times slower)? Could it be related to geth's update on version 6.2? Did anyone faced with similar issue?

[Q] This is very inefficient. If the node use much smaller hash-rate why on the background does the CPU consumes all the power? or just hash-rate calculation updated.

Thank you for your valuable time and help.

Answer 1

This issue has been solved.

@karalabe:

Missing hashrate was a regression. It was fixed in the latest stable release. Please update. As for the potential slowdown, we did switch out the C++ ethash code to a Go version a couple years back. CPU mining in general is not feasible, so there's not much point in striving to absolute max out performance. A well-enough performing CPU miner is enough for private/testnets.