Fix excessive mmap-ing in LMDB (cherrypick of #11513) #11516
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### Problem Core dumps collected on macOS are very large currently because they include all mmap'd data. According to `vmmap`, this is because LMDB is `mmap`'ing 1.7TB of data. And... it is! But not intentionally. ### Solution `ShardedLmdb` was not dividing the `max_size` by the number of shards, and since each shard used their own LMDB `Environment`, we were ending up with `16 * max_size` `mmap`'d. Additionally, we had set some of our databases to sizes that are well beyond what we expect the database to grow to when GC is running consistently. ### Result It is now possible to gather core dumps on macOS, which should assist in the debugging of pantsbuild#11364. [ci skip-build-wheels]
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Problem
Core dumps collected on macOS are very large currently because they include all mmap'd data. According to
vmmap, this is because LMDB ismmap'ing 1.7TB of data. And... it is! But not intentionally.Solution
ShardedLmdbwas not dividing themax_sizeby the number of shards, and since each shard used their own LMDBEnvironment, we were ending up with16 * max_sizemmap'd. Additionally, we had set some of our databases to sizes that are well beyond what we expect the database to grow to when GC is running consistently.Result
It is now possible to gather core dumps on macOS, which should assist in the debugging of #11364.
[ci skip-build-wheels]