I was bored on a train and I spent some amount of time trying to scratch
some nanoseconds off the Labels.Compare when running with stringlabels.
I would be ashamed to admit the real amount of time I spent on it.
The worst thing is, I can't really explain why this is performing so
much better, and someone should re-run the benchmarks on their machine
to confirm that it's not something related to general relativity because
the train is moving. I also added some extra real-life benchmark cases
with longer labelsets (these aren't the longest we have in production,
but kubernetes labelsets are fairly common in Prometheus so I thought it
would be nice to have them).
My benchmarks show this diff:
goos: darwin
goarch: arm64
pkg: github.com/prometheus/prometheus/model/labels
│ old │ new │
│ sec/op │ sec/op vs base │
Labels_Compare/equal 5.898n ± 0% 5.875n ± 1% -0.40% (p=0.037 n=10)
Labels_Compare/not_equal 11.78n ± 2% 11.01n ± 1% -6.54% (p=0.000 n=10)
Labels_Compare/different_sizes 4.959n ± 1% 4.906n ± 2% -1.05% (p=0.050 n=10)
Labels_Compare/lots 21.32n ± 0% 17.54n ± 5% -17.75% (p=0.000 n=10)
Labels_Compare/real_long_equal 15.06n ± 1% 14.92n ± 0% -0.93% (p=0.000 n=10)
Labels_Compare/real_long_different_end 25.20n ± 0% 24.43n ± 0% -3.04% (p=0.000 n=10)
geomean 11.86n 11.25n -5.16%
Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>
The current implementation of `InternStrings` will only save memory
when the whole set of labels is identical to one already seen, and this
cannot happen in the one place it is called from in Prometheus,
remote-write, which already detects identical series.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This function is called very frequently when executing PromQL functions,
and we can do it much more efficiently inside Labels.
In the common case that `__name__` comes first in the labels, we simply
re-point to start at the next label, which is nearly free.
`DropMetricName` is now so cheap I removed the cache - benchmarks show
everything still goes faster.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This reduces bulk and should avoid issues if a fix is made in one file
and not the other.
A few methods now call `Range()` instead of `range`, but nothing
performance-sensitive.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
* Labels: reduce allocations when creating from TSDB
When reading the WAL, by passing references into the buffer we can avoid
copying strings under `-tags stringlabels`.
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
Inline one call to `decodeString`, and skip decoding the value string
until we find a match for the name.
Do a quick check on the first character in each string,
and exit early if we've gone past - labels are sorted in order.
Also improve tests and benchmark:
* labels: test Get with varying lengths - it's not typical for Prometheus labels to all be the same length.
* extend benchmark with label not found
---------
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
Instead of unpacking every individual string, we skip to the point
where there is a difference, going 8 bytes at a time where possible.
Add benchmark for Compare; extend tests too.
---------
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
Co-authored-by: Oleg Zaytsev <mail@olegzaytsev.com>
This is a minor cosmetical change, but my IDE (and I guess many of them)
nests `labels_string.go` under `labels.go` because it assumes it's the
file generated by the `stringer` tool, which follows that naming
pattern.
Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>
