1545
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Ran 01 Jan 2016 04:36AM UTC

Jobs 1

Files 63

Run time 2s

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Build # 1545

Build Type

push

travis-ci

Committed by

ben-manes

Commit Message

Incremental reset analysis

The periodic reset ages the sketch every 10 * max_size increments. For
Caffeine this is handled in the background maintance cycle, but others
may expose that penalty to a caller. Thus its a concern of a seldomly
seen latency spike, which is a type of hiccup that can be hard to
debug.

An incremental reset ages the sketch as a gradual sweep, making the
penalty constant at a slight cost to the accuracy. However, as we use
the filter to detect heavy hitters and SLRU to find promising victims,
the impact should be minimal. Here we reset an array slot (16 counters)
every 16 additions. This is done in batches of 16 for efficiency and
should be similar to doing 1 counter reset per addition.

The result is a range of +/- 0.5% across a variety of traces [1]. This
spikes to 5.5% for MergeS as the worst case. That data was taken before
realizing that no-op increments were counted for reset. With this change
that MergeS case dropped to a 3% penalty. I haven't refreshed the data to
account for that fix, but this is enough to draw an early conclusion on
being a reasonable design choice.

[1] https://docs.google.com/spreadsheets/d/1G3deNz1gJCoXBE2IuraUSwLE7H_EMn4Sn2GU0HTpI5Y/edit?usp=sharing

Coverage Stats

4314 of 4594 relevant lines covered (93.91%)

0.94 hits per line

Jobs

ID	Job ID	Ran	Files	Coverage
1	1545.1 (TERM=dumb)	01 Jan 2016 04:36AM UTC	0	93.91	Travis Job 1545.1

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