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runtime: shrink time histogram buckets

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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>
This commit is contained in:
Michael Anthony Knyszek 2022-08-30 03:13:36 +00:00 • committed by Gopher Robot
parent 1fc83690e6
commit 87eda2a782
4 changed files with 162 additions and 131 deletions
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20
src/runtime/export_test.go
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@ -1228,22 +1228,28 @@ func MSpanCountAlloc(ms *MSpan, bits []byte) int {
}
const (
TimeHistSubBucketBits = timeHistSubBucketBits
TimeHistNumSubBuckets = timeHistNumSubBuckets
TimeHistNumSuperBuckets = timeHistNumSuperBuckets
TimeHistSubBucketBits = timeHistSubBucketBits
TimeHistNumSubBuckets = timeHistNumSubBuckets
TimeHistNumBuckets = timeHistNumBuckets
TimeHistMinBucketBits = timeHistMinBucketBits
TimeHistMaxBucketBits = timeHistMaxBucketBits
)
type TimeHistogram timeHistogram
// Counts returns the counts for the given bucket, subBucket indices.
// Returns true if the bucket was valid, otherwise returns the counts
// for the underflow bucket and false.
func (th *TimeHistogram) Count(bucket, subBucket uint) (uint64, bool) {
// for the overflow bucket if bucket > 0 or the underflow bucket if
// bucket < 0, and false.
func (th *TimeHistogram) Count(bucket, subBucket int) (uint64, bool) {
t := (*timeHistogram)(th)
i := bucket*TimeHistNumSubBuckets + subBucket
if i >= uint(len(t.counts)) {
if bucket < 0 {
return t.underflow.Load(), false
}
i := bucket*TimeHistNumSubBuckets + subBucket
if i >= len(t.counts) {
return t.overflow.Load(), false
}
return t.counts[i].Load(), true
}