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path: root/src/runtime/histogram_test.go
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2022-09-16runtime: shrink time histogram bucketsMichael Anthony Knyszek
There are lots of useless buckets with too much precision. Introduce a minimum level of precision with a minimum bucket bit. This cuts down on the size of a time histogram dramatically (~3x). Also, pick a smaller sub bucket count; we don't need 6% precision. Also, rename super-buckets to buckets to more closely line up with HDR histogram literature. Change-Id: I199449650e4b34f2a6dca3cf1d8edb071c6655c0 Reviewed-on: https://go-review.googlesource.com/c/go/+/427615 Run-TryBot: Michael Knyszek <mknyszek@google.com> Auto-Submit: Michael Knyszek <mknyszek@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com>
2022-02-10runtime: simplify histogram buckets considerablyMichael Anthony Knyszek
There was an off-by-one error in the time histogram buckets calculation that caused the linear sub-buckets distances to be off by 2x. The fix was trivial, but in writing tests I realized there was a much simpler way to express the calculation for the histogram buckets, and took the opportunity to do that here. The new bucket calculation also fixes the bug. Fixes #50732. Change-Id: Idae89986de1c415ee4e148f778e0e101ca003ade Reviewed-on: https://go-review.googlesource.com/c/go/+/380094 Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com> Trust: Michael Knyszek <mknyszek@google.com> Run-TryBot: Michael Knyszek <mknyszek@google.com>
2020-12-23runtime: shift timeHistogram buckets and allow negative durationsMichael Anthony Knyszek
Today, timeHistogram, when copied, has the wrong set of counts for the bucket that should represent (-inf, 0), when in fact it contains [0, 1). In essence, the buckets are all shifted over by one from where they're supposed to be. But this also means that the existence of the overflow bucket is wrong: the top bucket is supposed to extend to infinity, and what we're really missing is an underflow bucket to represent the range (-inf, 0). We could just always zero this bucket and continue ignoring negative durations, but that likely isn't prudent. timeHistogram is intended to be used with differences in nanotime, but depending on how a platform is implemented (or due to a bug in that platform) it's possible to get a negative duration without having done anything wrong. We should just be resilient to that and be able to detect it. So this change removes the overflow bucket and replaces it with an underflow bucket, and timeHistogram no longer panics when faced with a negative duration. Fixes #43328. Fixes #43329. Change-Id: If336425d7d080fd37bf071e18746800e22d38108 Reviewed-on: https://go-review.googlesource.com/c/go/+/279468 Run-TryBot: Michael Knyszek <mknyszek@google.com> TryBot-Result: Go Bot <gobot@golang.org> Trust: Michael Knyszek <mknyszek@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>
2020-10-26runtime: add timeHistogram typeMichael Anthony Knyszek
This change adds a concurrent HDR time histogram to the runtime with tests. It also adds a function to generate boundaries for use by the metrics package. For #37112. Change-Id: Ifbef8ddce8e3a965a0dcd58ccd4915c282ae2098 Reviewed-on: https://go-review.googlesource.com/c/go/+/247046 Run-TryBot: Michael Knyszek <mknyszek@google.com> TryBot-Result: Go Bot <gobot@golang.org> Trust: Michael Knyszek <mknyszek@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>