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perf: Clear cacheKV RAM if its too large #15767

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merged 4 commits into from
May 11, 2023

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ValarDragon
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@ValarDragon ValarDragon commented Apr 9, 2023

Description

Clear the CacheKV store's RAM if its too large. If the CacheKV's caches are too large, we've likely done some linear time workload.

The old design of never clearing this memory, meant significant RAM increases (all genesis size) throughout the entire InitGenesis process, unclear to me if this RAM overhead persisted in subsequent block processing. (Sometimes 2x large portions of genesis state, if the module does iteration and has a sorted cache) Most other RAM overheads throughout init genesis, are at least module-local for extra data.

This was 20+ GB reduced in peak Osmosis RAM usage during InitGenesis from a state export. This significantly reduces the RAM pressure.

This should also come in handy for Osmosis epoch blocks.


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@ValarDragon ValarDragon requested a review from a team as a code owner April 9, 2023 18:15
}
}

sort.Strings(keys)
store.deleteCaches()
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I think after the Write call, the whole cache store is discarded usually?

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@ValarDragon ValarDragon Apr 10, 2023

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Oh interesting. If so:

  • This is still a win, for getting the data discarded earlier. (rather than being held with the underlying DB's writes as well)
  • We should just always clear everything, rather than the old capacity preservation code then

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@mark-rushakoff mark-rushakoff left a comment

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I see a couple ways to improve readability here. I'm not familiar with the cachekv store yet, and I get the impression there are some subtleties I haven't fully identified yet.

store/cachekv/store.go Outdated Show resolved Hide resolved
store/cachekv/store.go Show resolved Hide resolved
keys := make([]string, 0, len(store.cache))
// Not the best. To reduce RAM pressure, we copy the values as well
// and clear out the old caches right after the copy.
sortedCache := make([]cEntry, 0, len(store.cache))
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Just an observation -- I assume this slice is often oversized, as it ideally match the number of dirty entries in the store.cache. That may be worth tuning in a separate PR.

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In general, the entire CacheKV store should just be rewritten entirely. We perenially run into performance issues due to some wack part of its design.

Its very overly complicated, for little reason

}
}

sort.Strings(keys)
store.deleteCaches()
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I think this method would read easier if resetting the caches happened before assigning into sortedCache, even if you need to store len(store.cache) first.

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I don't understand, you can only reset the caches, once you've grabbed a copy of the data?

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Friendly bump on this PR

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@kocubinski could we get your review in this?

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it looks good to me, it might be good to have a quick benchmark to test the difference.

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@alexanderbez alexanderbez left a comment

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LGTM @ValarDragon. I would say the arbitrary 100k value would warrant a benchmark though.

Comment on lines +108 to +110
for key := range store.cache {
delete(store.cache, key)
}

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Iteration over map

Iteration over map may be a possible source of non-determinism
Comment on lines +111 to +113
for key := range store.unsortedCache {
delete(store.unsortedCache, key)
}

Check warning

Code scanning / CodeQL

Iteration over map

Iteration over map may be a possible source of non-determinism
@@ -93,6 +93,28 @@ func (store *Store) Delete(key []byte) {
store.setCacheValue(key, nil, true)
}

func (store *Store) resetCaches() {
if len(store.cache) > 100_000 {
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@elias-orijtech elias-orijtech May 2, 2023

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In light of #15767 (comment) consider making this branch unconditional, that is, never use the cache clearing idiom.

The clearing was introduced as part of dbb9923, so I wonder how much performance is gained by the clearing itself. If not much, that's another reason to stop clearing.

@@ -103,44 +125,40 @@ func (store *Store) Write() {
return
}

type cEntry struct {
key string
val *cValue
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How about

type cEntry struct {
    key string
    value []byte
}

to shave off a field from each cache key? val.dirty is never referenced.

@ValarDragon ValarDragon added this pull request to the merge queue May 10, 2023
@github-merge-queue github-merge-queue bot removed this pull request from the merge queue due to failed status checks May 10, 2023
@tac0turtle tac0turtle added this pull request to the merge queue May 11, 2023
Merged via the queue into cosmos:main with commit d39f645 May 11, 2023
@tac0turtle tac0turtle deleted the dev/cachekv_clear_ram branch May 11, 2023 12:40
kocubinski pushed a commit that referenced this pull request May 11, 2023
Co-authored-by: Marko <marbar3778@yahoo.com>
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8 participants