Yonik Seeley created SOLR-10205:
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Summary: Evaluate and reduce BlockCache store failures
Key: SOLR-10205
URL: https://issues.apache.org/jira/browse/SOLR-10205
Project: Solr
Issue Type: Improvement
Security Level: Public (Default Security Level. Issues are Public)
Reporter: Yonik Seeley
The BlockCache is written such that requests to cache a block (BlockCache.store
call) can fail, making caching less effective. We should evaluate the impact
of this storage failure and potentially reduce the number of storage failures.
The implementation reserves a single block of memory. In store, a block of
memory is allocated, and then a pointer is inserted into the underling map. A
block is only freed when the underlying map evicts the map entry.
This means that when two store() operations are called concurrently (even under
low load), one can fail. This is made worse by the fact that concurrent maps
typically tend to amortize the cost of eviction over many keys (i.e. the actual
size of the map can grow beyond the configured maximum number of entries...
both the older ConcurrentLinkedHashMap and newer Caffeine do this). When this
is the case, store() won't be able to find a free block of memory, even if
there aren't any other concurrently operating stores.
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