TotalAlloc dropped in runtime/metrics

Marco A.

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Apr 20, 2021, 2:12:47 PM4/20/21

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Hi everyone,

I was considering using the new stable metrics interface with go 1.16 (https://golang.org/pkg/runtime/metrics/) for our program and I was also wondering why things like TotalAlloc (https://golang.org/pkg/runtime/#MemStats) had been dropped in the available metrics.

Any particular reasoning behind this?

Ian Lance Taylor

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Apr 20, 2021, 3:09:15 PM4/20/21

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Michael Knyszek

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Apr 20, 2021, 3:15:04 PM4/20/21

to Ian Lance Taylor, Marco A., golang-nuts

Oh gosh, I think TotalAlloc, Mallocs, and Frees are actually an oversight on my part. Sorry about that. They're very easy to add and I can probably even add them for this release.

Please do use the new runtime/metrics package!

Most of the other metrics should be there in some form (e.g. the divisions are a little different; they're meant to be more orthogonal to each other... GC pause latencies are now in a histogram) and new ones are going to be added in the next release and in the future. Also: today, it does not have the same stop-the-world penalty that ReadMemStats has, so I recommend it on that basis.

Michael Knyszek

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Apr 20, 2021, 3:29:28 PM4/20/21

to Ian Lance Taylor, Marco A., golang-nuts

Oh, actually, you can compute Mallocs and Frees from allocs-by-size and frees-by-size (summing the total # of samples). You can only estimate TotalAlloc though, which is genuinely missing.

Marco A.

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Apr 21, 2021, 5:32:16 AM4/21/21

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Thanks Michael, do not worry about TotalAlloc.. we do have that metric to replace somehow but we might even think about dropping it completely.

I was honestly wondering if TotalAlloc (cumulative bytes allocated for heap objects) is a useful metric to have at all since Go uses garbage collection. I don't believe this could even be useful for heap fragmentation, but I'd like to hear your thoughts on the matter since you're obviously more experienced than me in this regard.

Michael Knyszek

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Apr 29, 2021, 5:55:50 PM4/29/21

to Ian Lance Taylor, Marco A., golang-nuts

Hi Marco, https://go-review.googlesource.com/c/go/+/312431 just landed and should resolve the issue for Go 1.17.

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