EntityIterable cache doesn't appear to respect ENTITY_ITERABLE_CACHE_SIZE

[Dan Gravell (gravelld)]

I'm doing this:

    PersistentEntityStoreConfig config = new PersistentEntityStoreConfig();
    config = config.setEntityIterableCacheSize(100);
    this.entityStore = PersistentEntityStores.newInstance(config, env, getClass().getSimpleName());

I then load some data into my Xodus entity store and take a heap dump at the end.

No matter if I setEntityIterableCacheSize or leave it at the default the end memory consumption is the same - about 15MB. The same structure is built by the EntityIterableCache - a PersistentLinkedHashMap with the same number of levels and objects inside. I can see NonAdjustablePersistentObjectCache has the size correctly passed through.

I can see there's a RemoveEldestFunction which appears to do cache eviction. It asks for the size of the contained map, and this is implemented by RootTableNode which currently has its size set to 5 - thus it never evicts.

Do I misunderstand the purpose of this setting? I guess so.

(Aside)
MAX_DEFAULT_ENTITY_ITERABLE_CACHE_SIZE has an odd name - it appears to not be a maximum but a minimum:

    return Math.max((int) (Runtime.getRuntime().maxMemory() >> 20), MAX_DEFAULT_ENTITY_ITERABLE_CACHE_SIZE);

(i.e. a number related to the heap size or MAX_DEFAULT_ENTITY_ITERABLE_CACHE_SIZE, whichever is larger)

[Andrii Lomakin (andrii0lomakin)]

Hi Dan Gravell (@gravelld) you misunderstood object which you should observe, it should be ConcurrentObjectCache instance. Which field do you mean when you mention PersistentLinkedHashMap ?

[Dan Gravell (gravelld)]

I saw ConcurrentLongObjectCache (note the additional "Long") but I thought that was the Log cache, not the EntityIterableCache. I thought these were two separate things. The ConcurrentLongObjectCache I see is stored within SharedLogCache.

The EntityIterableCache I'm referring to is stored in the iterableCache member of PersistentEntityStoreImpl. The EntityIterableCache then has a cache -> root and then there's a Root instance which constains the Persistentx hashmaps/hashsets.

This iterable cache always weighs in at a hefty 12MB so I was hoping to reduce its size (I'm running in a constrained environment). And besides - I thought the setEntityIterableCacheSize referred to a cache of EntityIterables and was nothing to do with the Log.

The Log caching sizing does work, btw. For that I use:

    EnvironmentConfig envConfig = new EnvironmentConfig();
    envConfig = envConfig.setMemoryUsage((1024 * 1024) * 2);

[Andrii Lomakin (andrii0lomakin)]

Dan Gravell (@gravelld) classes you list are part of the query processing, not the cache itself. If you wish us to investigate this issue, please fill the case in the bug tracker and provide a reproducer. As for now, it is hard to understand if the problem does exist. We use the given parameter daily
on many installations, so we need to double-check that the issue is present.

[Dan Gravell (gravelld)]

Thanks - I'll revisit the issue assuming it's a query that is being processed or used.