Make Cache More Memory Efficient #77546
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No need to keep counters per segment when we only use them in aggregate. Also, removed a few spots of using needless indirection by making segments reference the cache itself directly and saved a bunch of empty maps for idle caches on e.g. rarely used indices.
original-brownbear
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>non-issue
:Core/Infra/Core
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Pinging @elastic/es-core-infra (Team:Core/Infra) |
grcevski
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Sep 10, 2021
| @@ -742,25 +733,29 @@ public long getEvictions() { | |||
| } | |||
| } | |||
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| private boolean promote(Entry<K, V> entry, long now) { | |||
| boolean promoted = true; | |||
| private void promote(Entry<K, V> entry, long now) { | |||
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Just a minor thought here, splitting this method to avoid double locking may not be worth the complexity. ReentrantLock will check if a lock is already owned by the same thread and avoid the compare and set operation. There's still going to be a volatile int field increment, but it should be relatively inexpensive.
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Fair point :) reverted that part of the change
grcevski
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Sep 13, 2021
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Thanks Nikola! |
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No need to keep counters per segment when we only use them in aggregate. Also, removed a few spots of using needless indirection by making segments reference the cache itself directly and saved a bunch of empty maps for idle caches on e.g. rarely used indices.
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No need to keep counters per segment when we only use them in aggregate. Also, removed a few spots of using needless indirection by making segments reference the cache itself directly and saved a bunch of empty maps for idle caches on e.g. rarely used indices.
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Found the memory savings while looking at some heap dumps and added the indirection savings on top:
No need to keep counters per segment when we only use them in aggregate.
Also, removed a few spots of using needless indirection by making
segments reference the cache itself directly and saved a bunch of empty maps
for idle caches on e.g. rarely used indices.
This halves the size of an empty cache (I think it was ~110k to ~60k in the empty case) which isn't a massive saving but also not entirely irrelevant when thinking about large index counts per node (+ it speeds up tests a little by saving 10M+ on heap during most internal cluster tests from all kinds of empty caches :)).