map_hash_bucket_size, map_hash_max_size, and memory usage

Maxim Dounin mdounin at
Wed Nov 5 12:26:05 UTC 2014


On Tue, Nov 04, 2014 at 12:27:51PM -0500, abstein2 wrote:

> I was hoping someone could clarify how exactly map_hash_bucket_size and
> map_hash_max_size should be set and the impact it has on memory.
> For map_hash_bucket_size, it says it should be a multiple of the processor's
> line cache size. Under what circumstances does it make sense or would it be
> necessary to move away from the default cache size?
> For map_hash_max_size, is this just the maximum size of the hash? If so,
> what is the metric: bytes? potential options? something else? Is it viewed
> as the maximum size of all maps or just each specific map directive?
> Also, do either of these values impact the memory that nginx uses? For
> example, if I have 200 maps will ones with a higher map_hash_bucket_size use
> more memory than one with a lower map_hash_bucket_size? Or a higher
> map_hash_max_size?

Some details about configuring of hashes can be found here:

Maxim Dounin

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