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enable full percentile spectrum analysis on latency #100

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yossigo merged 4 commits into from
Aug 12, 2020
Merged

enable full percentile spectrum analysis on latency #100

yossigo merged 4 commits into from
Aug 12, 2020

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@filipecosta90
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@filipecosta90 filipecosta90 commented Nov 10, 2019 •
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Full percentile spectrum analysis

Fixes: #68
This PR enable full percentile spectrum analysis on query latency so that we can fully understand the performance and stability characteristics of the system we are measuring.

Right now memtier_benchmark is displaying single values targets like the average.
Considering that latency does not obey a normal distribution we should enable ourselves to do full percentile spectrum analysis. Just looking at a number might be misleading.

A useful visualization for pointing out the folly of chasing a mean measurement is illustrated below - they have nearly identical simple descriptive statistics, yet have very different distributions and appear very different when graphed.

image

Source: https://en.wikipedia.org/wiki/Anscombe%27s_quartet

Enabling full percentile latencies on memtier_benchmark:

The previous features can be applied with the changes added on this PR using the following added options:

      --hdr-file-prefix=FILE     Prefix of HDR Latency Histogram output files, if not set, will not save latency histogram files
      --print-percentiles          Specify which percentiles info to print on the results table (by default prints percentiles: 50,99,99.9)

yossigo
yossigo suggested changes Nov 17, 2019
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@filipecosta90 Thanks for this PR, I've went through most of it (maybe not enough in detail in some parts though) and added a few comments.
Nitpicking: there are some extra white space and code style issues in this PR, it would be a good idea to re-review it and clean it up.

yaacovhazan-Redislabs
yaacovhazan-Redislabs suggested changes Nov 21, 2019
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yaacovhazan-Redislabs
yaacovhazan-Redislabs suggested changes Dec 4, 2019
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@filipecosta90 filipecosta90 changed the title enable full percentile spectrum analysis on latency. enable maintaining fixed rps during query benchmarks enable full percentile spectrum analysis on latency Jan 27, 2020
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filipecosta90 commented Aug 9, 2020

Hi there @yossigo and @yaacovhazan-Redislabs I've pruned the PR and I believe it's ready for a new review.
I've updated the hdrhistogram to the latest official one ( v0.11.0 ), added a test case for the added features, and extended the PR to store per second latency/throughput metrics at the output json ( The stored percentiles comes from the --print-percentiles property ). Here is a snippet:

,"ALL STATS":{
		"Runtime":{
			"Start time": 1597016193374
			,"Finish time": 1597016207579
			,"Total duration": 14205
			,"Time unit": "MILLISECONDS"
			}
		,"Sets":{
			"Count": 182000
			,"Ops/sec": 12812.51
			,"Hits/sec": 0.00
			,"Misses/sec": 0.00
			,"Latency": 1.419
			,"Average Latency": 1.419
			,"Min Latency": 0.032
			,"Max Latency": 14.415
			,"KB/sec": 986.79
			,"Time-Serie":{
				"0":{
					"Count": 14225
					,"Average Latency": 1.29
					,"Min Latency": 0.54
					,"Max Latency": 6.43
					,"p50.00": 1.17
					,"p99.00": 3.73
					,"p99.90": 4.96
					}
				,"1":{
					"Count": 14739
					,"Average Latency": 1.23
					,"Min Latency": 0.10
					,"Max Latency": 7.78
					,"p50.00": 1.20
					,"p99.00": 2.62
					,"p99.90": 5.86
					}
(...)

WDYT?

@yossigo yossigo merged commit 145c02b into redis:master Aug 12, 2020
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yossigo commented Aug 12, 2020

@filipecosta90 Thanks a lot for this effort! It's a great improvement and definitely worth the effort and time invested in it.

@filipecosta90 filipecosta90 mentioned this pull request Aug 12, 2020
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Provide more latency data in results

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@filipecosta90 @yossigo @yaacovhazan-Redislabs