Geth uses 100% CPU even with 1 thread active

[opelykhtabia]

System information

Geth version: 1.9.6
OS & Version: Linux (Ubuntu 18.04)
Commit hash : bd05968

Expected behaviour

Only 1 thread is used.

Actual behaviour

All CPU threads (8) are used with a 100% load.

Steps to reproduce the behaviour

Run geth with parameters
--mine --minerthreads "1"
or
--mine --minerthreads 1

[jeffwalsh]

That command is deprecrated:

MinerLegacyThreadsFlag = cli.IntFlag{
		Name:  "minerthreads",
		Usage: "Number of CPU threads to use for mining (deprecated, use --miner.threads)",
		Value: 0,
	}

Use geth --mine --miner.threads=1 instead I believe.

[jeffwalsh]

actually, the legacy one should still work, so i dont know if that would resolve your issue.
it says its deprected but its still used unless --miner.threads is also used
in cmd/geth/main.go:

		threads := ctx.GlobalInt(utils.MinerLegacyThreadsFlag.Name)
		if ctx.GlobalIsSet(utils.MinerThreadsFlag.Name) {
			threads = ctx.GlobalInt(utils.MinerThreadsFlag.Name)
		}

[karalabe]

Ah, I think I know what the issue is. It's probably still constructing the mining DAG. That takes a few minutes and it's multi-threaded, so it will use up all your cores until it finishes. Mining itself will be single threaded afterwards.

You can verify by looking at the logs. If it prints something along the lines of Generating DAG in progress, it's still building the dataset on multiple threads.

[holiman]

Verified that when you already have the dag, it's only one processor at 100%