cmd/geth: use automaxprocs to apply cpu quota correctly (#21)

### Description

upstream PR:
[go-ethereum#27506](ethereum/go-ethereum#27506)

As discussed with @rjl493456442 offline, if Geth was running in a
container with CPU quota(set with cgroup limiting), and runtime.NumCPU
returns the host's CPU cores(maybe bigger than the docker's setting),
which may result in more Golang runtime schedule and context switch.

So I'm using the
[uber/atomaxprocs](https://github.com/uber-go/automaxprocs) package to
return the correct cpu quota.

cmd/geth/main.go

@@ -43,6 +43,9 @@ import (
 	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
 	_ "github.com/ethereum/go-ethereum/eth/tracers/native"
 
+	// Automatically set GOMAXPROCS to match Linux container CPU quota.
+	_ "go.uber.org/automaxprocs"
+
 	"gopkg.in/urfave/cli.v1"
 )
 

go.mod

@@ -59,6 +59,7 @@ require (
 	github.com/tendermint/iavl v0.12.0
 	github.com/tendermint/tendermint v0.31.12
 	github.com/tyler-smith/go-bip39 v1.0.1-0.20181017060643-dbb3b84ba2ef
+	go.uber.org/automaxprocs v1.5.2
 	golang.org/x/crypto v0.5.0
 	golang.org/x/sync v0.1.0
 	golang.org/x/sys v0.5.0

go.sum

@@ -426,6 +426,7 @@ github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINE
 github.com/pkg/term v0.0.0-20180730021639-bffc007b7fd5/go.mod h1:eCbImbZ95eXtAUIbLAuAVnBnwf83mjf6QIVH8SHYwqQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prashantv/gostub v1.1.0 h1:BTyx3RfQjRHnUWaGF9oQos79AlQ5k8WNktv7VGvVH4g=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v1.0.0/go.mod h1:db9x61etRT2tGnBNRi70OPL5FsnadC4Ky3P0J6CfImo=
 github.com/prometheus/client_golang v1.7.1/go.mod h1:PY5Wy2awLA44sXw4AOSfFBetzPP4j5+D6mVACh+pe2M=
@@ -529,6 +530,8 @@ go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.3/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.4/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.uber.org/atomic v1.3.2/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
+go.uber.org/automaxprocs v1.5.2 h1:2LxUOGiR3O6tw8ui5sZa2LAaHnsviZdVOUZw4fvbnME=
+go.uber.org/automaxprocs v1.5.2/go.mod h1:eRbA25aqJrxAbsLO0xy5jVwPt7FQnRgjW+efnwa1WM0=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.9.1/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=