R4R: CacheKVStore keep sorted items

[mossid]

closes: #2286

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• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: clog add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
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• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[mossid]

make test_sim_gaia_test took 234 seconds, master branch took 233 seconds.

• 5cb6fe5 took 226 seconds

[codecov]

Codecov Report

Merging #4265 into master will increase coverage by 0.07%.
The diff coverage is 93.65%.

@@            Coverage Diff             @@
##           master    #4265      +/-   ##
==========================================
+ Coverage   59.38%   59.46%   +0.07%     
==========================================
  Files         214      214              
  Lines       14533    14569      +36     
==========================================
+ Hits         8631     8664      +33     
- Misses       5264     5267       +3     
  Partials      638      638

[hendrikhofstadt]

@mossid Why was this closed ?

I benchmarked this on one of our state migrators and the improvement was very significant.

[mossid]

@hendrikhofstadt the gaiasim test didnt show performance improvement, so I thought it didnt work. Turns out most of the execution time in gaiasim is of the golang memory manager. Reopening the pr. Thanks for testing, do you have a benchmark result?

[alessio]

Looks good to me. I think it's worth a mention in the changelog:

clog add improvements sdk

[alexanderbez]

Nice work @mossid, thanks! I've added a pending log entry and also I added a benchmark suite. Although the benchmark suite doesn't add any new items, it just solely benchmarks the iterator. Still, amazing improvement by not sorting every time.

current master:

goos: darwin
goarch: amd64
pkg: github.com/cosmos/cosmos-sdk/store/cachekv
BenchmarkCacheKVStoreIterator500-4      	  100000	    308614 ns/op
BenchmarkCacheKVStoreIterator1000-4     	   50000	    629593 ns/op
BenchmarkCacheKVStoreIterator10000-4    	    2000	  15185275 ns/op
BenchmarkCacheKVStoreIterator50000-4    	     500	  75376816 ns/op
BenchmarkCacheKVStoreIterator100000-4   	     200	 183787254 ns/op

this PR:

goos: darwin
goarch: amd64
pkg: github.com/cosmos/cosmos-sdk/store/cachekv
BenchmarkCacheKVStoreIterator500-4      	 1000000	     45666 ns/op
BenchmarkCacheKVStoreIterator1000-4     	  300000	     84568 ns/op
BenchmarkCacheKVStoreIterator10000-4    	   20000	   1447204 ns/op
BenchmarkCacheKVStoreIterator50000-4    	    2000	  17269444 ns/op
BenchmarkCacheKVStoreIterator100000-4   	    1000	  29898436 ns/op

[alexanderbez]

wow. good catch.