commit a1c56757aa42df2baa8ff0c660a0ce2b468f1723
author Ian Cottrell <iancottrell@google.com> Fri Feb 28 22:55:50 2020 -0500
committer Ian Cottrell <iancottrell@google.com> Tue Mar 03 22:56:24 2020 +0000
tree 7fe9a7f88a28e885db14557319232eba65a735de
parent ae19ec714359fc93998078066daf8cb98ee23fb7

internal/telemetry: remove the concept of a Tagger

The Tagger interface allowed for specifying a key in a tag list and having the
value be aquired from the context automatically. It was almost never used, and
the alternative (using the key to get the value) is not that much more long
winded, so it was not holding it's own weight from a complexity persective alone
but the performance cost of having to use a list of interface rather than a list
of tags was very large. See the benchstat improvements below for the difference
it makes to both speed and memory usage, especially in the no exporter case.

name                 old time/op    new time/op    delta
Baseline-8              341ns ± 2%     342ns ± 1%     ~     (p=0.139 n=19+18)
LoggingNoExporter-8    2.46µs ± 5%    1.97µs ± 3%  -19.88%  (p=0.000 n=19+20)
Logging-8              13.3µs ± 2%    12.8µs ± 2%   -3.42%  (p=0.000 n=17+20)
LoggingStdlib-8        5.39µs ± 6%    5.34µs ± 3%     ~     (p=0.692 n=20+19)

name                 old alloc/op   new alloc/op   delta
Baseline-8              80.0B ± 0%     80.0B ± 0%     ~     (all equal)
LoggingNoExporter-8      728B ± 0%      440B ± 0%  -39.56%  (p=0.000 n=20+20)
Logging-8              2.75kB ± 0%    2.46kB ± 0%  -10.53%  (p=0.000 n=17+20)
LoggingStdlib-8          568B ± 0%      568B ± 0%     ~     (all equal)

name                 old allocs/op  new allocs/op  delta
Baseline-8               5.00 ± 0%      5.00 ± 0%     ~     (all equal)
LoggingNoExporter-8      32.0 ± 0%      23.0 ± 0%  -28.12%  (p=0.000 n=20+20)
Logging-8                88.0 ± 0%      79.0 ± 0%  -10.23%  (p=0.000 n=20+20)
LoggingStdlib-8          28.0 ± 0%      28.0 ± 0%     ~     (all equal)

Change-Id: Ic203ad0c5de7451348976b999a0d038ac532dc39
Reviewed-on: https://go-review.googlesource.com/c/tools/+/221737
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>