* perf: store/cachekv: avoid a map lookup if unnecessary, clear maps fast (#10486)
We can shave off some milliseconds, but also cut down some Megabytes of
RAM consumed by only requesting from the cache if needed, but also using
the map clearing idiom which is recognized by the compiler to make fast
code.
Noticed in profiles from Tharsis' Ethermint per https://github.com/tharsis/ethermint/issues/710
- Before
* Memory profiles
```shell
19.50MB 19.50MB 134: store.cache = make(map[string]*cValue)
18.50MB 18.50MB 135: store.deleted = make(map[string]struct{})
15.50MB 15.50MB 136: store.unsortedCache = make(map[string]struct{})
```
* CPU profiles
```go
. . 118: // TODO: Consider allowing usage of Batch, which would allow the write to
. . 119: // at least happen atomically.
150ms 150ms 120: for _, key := range keys {
220ms 3.64s 121: cacheValue := store.cache[key]
. . 122:
. . 123: switch {
. 250ms 124: case store.isDeleted(key):
. . 125: store.parent.Delete([]byte(key))
210ms 210ms 126: case cacheValue.value == nil:
. . 127: // Skip, it already doesn't exist in parent.
. . 128: default:
240ms 27.94s 129: store.parent.Set([]byte(key), cacheValue.value)
. . 130: }
. . 131: }
...
10ms 60ms 134: store.cache = make(map[string]*cValue)
. 40ms 135: store.deleted = make(map[string]struct{})
. 50ms 136: store.unsortedCache = make(map[string]struct{})
. 110ms 137: store.sortedCache = dbm.NewMemDB()
```
- After
* Memory profiles
```shell
. . 130: // Clear the cache using the map clearing idiom
. . 131: // and not allocating fresh objects.
. . 132: // Please see https://bencher.orijtech.com/perfclinic/mapclearing/
. . 133: for key := range store.cache {
. . 134: delete(store.cache, key)
. . 135: }
. . 136: for key := range store.deleted {
. . 137: delete(store.deleted, key)
. . 138: }
. . 139: for key := range store.unsortedCache {
. . 140: delete(store.unsortedCache, key)
. . 141: }
```
* CPU profiles
```shell
. . 111: // TODO: Consider allowing usage of Batch, which would allow the write to
. . 112: // at least happen atomically.
110ms 110ms 113: for _, key := range keys {
. 210ms 114: if store.isDeleted(key) {
. . 115: // We use []byte(key) instead of conv.UnsafeStrToBytes because we cannot
. . 116: // be sure if the underlying store might do a save with the byteslice or
. . 117: // not. Once we get confirmation that .Delete is guaranteed not to
. . 118: // save the byteslice, then we can assume only a read-only copy is sufficient.
. . 119: store.parent.Delete([]byte(key))
. . 120: continue
. . 121: }
. . 122:
50ms 2.45s 123: cacheValue := store.cache[key]
910ms 920ms 124: if cacheValue.value != nil {
. . 125: // It already exists in the parent, hence delete it.
120ms 29.56s 126: store.parent.Set([]byte(key), cacheValue.value)
. . 127: }
. . 128: }
. . 129:
. . 130: // Clear the cache using the map clearing idiom
. . 131: // and not allocating fresh objects.
. . 132: // Please see https://bencher.orijtech.com/perfclinic/mapclearing/
. 210ms 133: for key := range store.cache {
. . 134: delete(store.cache, key)
. . 135: }
. 10ms 136: for key := range store.deleted {
. . 137: delete(store.deleted, key)
. . 138: }
. 170ms 139: for key := range store.unsortedCache {
. . 140: delete(store.unsortedCache, key)
. . 141: }
. 260ms 142: store.sortedCache = dbm.NewMemDB()
. 10ms 143:}
```
Fixes#10487
Updates https://github.com/tharsis/ethermint/issues/710
(cherry picked from commit 5399e72f32)
# Conflicts:
# CHANGELOG.md
* fix conflicts
Co-authored-by: Emmanuel T Odeke <emmanuel@orijtech.com>
Co-authored-by: Aleksandr Bezobchuk <aleks.bezobchuk@gmail.com>
14cd943a2e