cmd/go: gather cache age and reuse distribution statistics

[rsc]

We'd like to get a sense of how long typical cache entries hang around and are still useful to reuse, so we can decide what the expiration policy is. If you've been running go at master for the past month, please run:

go get -u rsc.io/gocachelogstat
gocachelogstat

and then paste the output in a comment below.

[rsc]

cache age: 32.73 days
action cache: 1964886 bytes, 1171632 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.00 days
	30% 0.00 days
	40% 0.01 days
	50% 0.02 days
	60% 0.05 days
	70% 0.08 days
	80% 0.27 days
	90% 0.57 days
	95% 2.16 days
	99% 2.20 days
	99.9% 2.21 days
	max 4.99 days
data cache: 1629193459 bytes, 876223874 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.00 days
	30% 0.00 days
	40% 0.02 days
	50% 0.05 days
	60% 0.18 days
	70% 0.33 days
	80% 2.16 days
	90% 11.86 days
	95% 23.25 days
	99% 23.97 days
	99.9% 23.99 days
	max 31.93 days

[aclements]

cache age: 26.73 days
action cache: 833910 bytes, 356818 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.00 days
	30% 0.00 days
	40% 0.00 days
	50% 0.00 days
	60% 0.00 days
	70% 0.00 days
	80% 0.01 days
	90% 0.05 days
	95% 0.15 days
	99% 1.49 days
	99.9% 1.50 days
	max 1.50 days
data cache: 1093251353 bytes, 406148966 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.00 days
	30% 0.00 days
	40% 0.00 days
	50% 0.00 days
	60% 0.05 days
	70% 1.22 days
	80% 5.23 days
	90% 6.17 days
	95% 8.86 days
	99% 18.98 days
	99.9% 18.98 days
	max 18.98 days

[bradfitz]

cache age: 20.92 days
action cache: 1284668 bytes, 585662 reused
        reuse time percentiles
        10% 0.00 days
        20% 0.00 days
        30% 0.02 days
        40% 0.04 days
        50% 0.09 days
        60% 0.16 days
        70% 0.88 days
        80% 1.50 days
        90% 2.41 days
        95% 3.90 days
        99% 6.14 days
        99.9% 6.27 days
        max 6.32 days
data cache: 1138671862 bytes, 523494735 reused
        reuse time percentiles
        10% 0.00 days
        20% 0.03 days
        30% 0.15 days
        40% 1.01 days
        50% 2.18 days
        60% 3.29 days
        70% 4.19 days
        80% 13.88 days
        90% 14.17 days
        95% 15.84 days
        99% 17.35 days
        99.9% 17.83 days
        max 20.87 days

[cespare]

What's the command that generates these reports?

[dsnet]

cache age: 25.93 days
action cache: 132440 bytes, 49280 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.00 days
	30% 0.00 days
	40% 0.01 days
	50% 0.01 days
	60% 0.02 days
	70% 0.03 days
	80% 0.03 days
	90% 0.04 days
	95% 0.04 days
	99% 0.04 days
	99.9% 0.04 days
	max 0.04 days
data cache: 101709358 bytes, 36986860 reused
	reuse time percentiles
	10% 0.00 days
	20% 0.01 days
	30% 0.01 days
	40% 0.02 days
	50% 0.03 days
	60% 0.04 days
	70% 2.04 days
	80% 2.08 days
	90% 2.08 days
	95% 17.10 days
	99% 20.08 days
	99.9% 20.09 days
	max 20.09 days

[RLH]

Not working at tip so I'm getting this.
rlh@rlh:/work/go/src$ go get -u rsc.io/gocachelogstat
rlh@rlh:/work/go/src$ gocachelogstat
gocachelogstat:go env GOCACHE: no output (old Go version?)
rlh@rlh:~/work/go/src$

[OneOfOne]

cache age: 28.05 days
action cache: 1420804 bytes, 200970 reused
        reuse time percentiles
        10% 0.00 days
        20% 0.00 days
        30% 0.00 days
        40% 0.00 days
        50% 0.00 days
        60% 0.00 days
        70% 0.01 days
        80% 0.01 days
        90% 0.86 days
        95% 5.83 days
        99% 5.83 days
        99.9% 5.91 days
        max 5.99 days
data cache: 997482283 bytes, 126848266 reused
        reuse time percentiles
        10% 0.00 days
        20% 0.00 days
        30% 0.00 days
        40% 0.00 days
        50% 0.01 days
        60% 0.19 days
        70% 0.86 days
        80% 1.04 days
        90% 5.05 days
        95% 6.88 days
        99% 19.95 days
        99.9% 20.03 days
        max 20.03 days

edit updated gocachelogstat:

cache age: 28.79 days
action cache: 1421112 bytes, 200970 reused
        reuse time percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.00 days
                60% 0.00 days
                70% 0.01 days
                80% 0.01 days
                90% 0.86 days
                95% 5.83 days
                99% 5.83 days
                99.9% 5.91 days
                max 5.99 days
        reuse time delta percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.00 days
                60% 0.00 days
                70% 0.00 days
                80% 0.00 days
                90% 0.01 days
                95% 0.86 days
                99% 5.83 days
                99.9% 5.91 days
                max 5.99 days
data cache: 997513519 bytes, 126848266 reused
        reuse time percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.01 days
                60% 0.19 days
                70% 0.86 days
                80% 1.04 days
                90% 5.05 days
                95% 6.88 days
                99% 19.95 days
                99.9% 20.03 days
                max 20.03 days
        reuse time delta percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.00 days
                60% 0.00 days
                70% 0.00 days
                80% 0.00 days
                90% 0.01 days
                95% 0.53 days
                99% 5.83 days
                99.9% 5.91 days
                max 5.99 days

[rsc]

@cespare, see top comment on issue (wasn't emailed).

[rsc]

@RLH, if you're not working at tip don't worry about it - this only affects the new caching code at tip. Thanks though.

[davecheney]

cache age: 17.09 days
action cache: 472164 bytes, 131516 reused
        reuse time percentiles
                10% 2.92 days
                20% 2.95 days
                30% 3.73 days
                40% 3.84 days
                50% 4.76 days
                60% 9.08 days
                70% 9.11 days
                80% 9.22 days
                90% 11.01 days
                95% 11.26 days
                99% 12.38 days
                99.9% 17.00 days
                max 17.08 days
        reuse time delta percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.00 days
                60% 0.00 days
                70% 0.00 days
                80% 0.00 days
                90% 0.01 days
                95% 0.06 days
                99% 1.15 days
                99.9% 4.25 days
                max 16.19 days
data cache: 409366597 bytes, 114953359 reused
        reuse time percentiles
                10% 2.92 days
                20% 2.95 days
                30% 3.73 days
                40% 3.84 days
                50% 4.76 days
                60% 9.08 days
                70% 9.12 days
                80% 9.22 days
                90% 11.01 days
                95% 11.26 days
                99% 12.38 days
                99.9% 17.00 days
                max 17.08 days
        reuse time delta percentiles
                10% 0.00 days
                20% 0.00 days
                30% 0.00 days
                40% 0.00 days
                50% 0.00 days
                60% 0.00 days
                70% 0.00 days
                80% 0.00 days
                90% 0.00 days
                95% 0.01 days
                99% 0.76 days
                99.9% 4.25 days
                max 16.19 days

[titanous]

cache age: 27.32 days
action cache: 83468 bytes, 53900 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.02 days
		50% 0.02 days
		60% 0.02 days
		70% 0.03 days
		80% 0.98 days
		90% 0.98 days
		95% 9.03 days
		99% 9.98 days
		99.9% 9.98 days
		max 9.98 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.00 days
		95% 0.86 days
		99% 0.95 days
		99.9% 6.99 days
		max 6.99 days
data cache: 59216559 bytes, 29841680 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.02 days
		40% 0.02 days
		50% 0.02 days
		60% 0.03 days
		70% 0.98 days
		80% 6.06 days
		90% 9.03 days
		95% 9.98 days
		99% 9.98 days
		99.9% 9.98 days
		max 9.98 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.00 days
		95% 0.02 days
		99% 0.95 days
		99.9% 6.99 days
		max 6.99 days

[robpike]

cache age: 29.02 days
action cache: 801878 bytes, 338646 reused
	reuse time percentiles
		10% 0.01 days
		20% 0.01 days
		30% 0.87 days
		40% 0.93 days
		50% 0.97 days
		60% 1.01 days
		70% 1.02 days
		80% 1.08 days
		90% 1.10 days
		95% 5.10 days
		99% 5.15 days
		99.9% 6.01 days
		max 6.11 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.00 days
		95% 0.02 days
		99% 0.87 days
		99.9% 3.16 days
		max 6.11 days
data cache: 445888150 bytes, 199539663 reused
	reuse time percentiles
		10% 0.01 days
		20% 0.91 days
		30% 0.99 days
		40% 1.02 days
		50% 5.10 days
		60% 14.12 days
		70% 15.05 days
		80% 15.12 days
		90% 15.19 days
		95% 15.20 days
		99% 19.24 days
		99.9% 19.26 days
		max 24.04 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.00 days
		95% 0.00 days
		99% 0.79 days
		99.9% 3.16 days
		max 24.03 days

[stemar94]

cache age: 32.15 days
action cache: 326172 bytes, 17402 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.01 days
		30% 0.01 days
		40% 0.03 days
		50% 0.08 days
		60% 0.09 days
		70% 0.17 days
		80% 0.17 days
		90% 0.17 days
		95% 0.21 days
		99% 0.21 days
		99.9% 0.21 days
		max 0.21 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.01 days
		70% 0.01 days
		80% 0.03 days
		90% 0.08 days
		95% 0.09 days
		99% 0.21 days
		99.9% 0.21 days
		max 0.21 days
data cache: 476840745 bytes, 20714746 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.01 days
		30% 0.01 days
		40% 0.03 days
		50% 0.08 days
		60% 0.09 days
		70% 0.17 days
		80% 0.17 days
		90% 0.17 days
		95% 0.21 days
		99% 0.21 days
		99.9% 0.21 days
		max 0.21 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.01 days
		70% 0.01 days
		80% 0.03 days
		90% 0.08 days
		95% 0.09 days
		99% 0.21 days
		99.9% 0.21 days
		max 0.21 days

[rhysh]

cache age: 25.15 days
action cache: 944790 bytes, 756756 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.40 days
		70% 4.22 days
		80% 4.36 days
		90% 4.40 days
		95% 4.42 days
		99% 4.45 days
		99.9% 4.45 days
		max 4.45 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.02 days
		95% 0.06 days
		99% 2.09 days
		99.9% 3.67 days
		max 4.45 days
data cache: 745875378 bytes, 469831660 reused
	reuse time percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.22 days
		60% 4.10 days
		70% 4.39 days
		80% 14.18 days
		90% 18.15 days
		95% 18.18 days
		99% 18.23 days
		99.9% 18.23 days
		max 18.23 days
	reuse time delta percentiles
		10% 0.00 days
		20% 0.00 days
		30% 0.00 days
		40% 0.00 days
		50% 0.00 days
		60% 0.00 days
		70% 0.00 days
		80% 0.00 days
		90% 0.00 days
		95% 0.02 days
		99% 0.55 days
		99.9% 3.67 days
		max 12.69 days