Add SYNAPSE_CACHE_FACTOR to README

This commit is contained in:
Erik Johnston 2016-03-02 14:03:10 +00:00
parent 374f9b2f07
commit dda2058d90

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@ -566,3 +566,20 @@ Building internal API documentation::
python setup.py build_sphinx
Halp!! Synapse eats all my RAM!
===============================
Synapse's architecture is quite RAM hungry currently - we deliberately
cache a lot of recent room data and metadata in RAM in order to speed up
common requests. We'll improve this in future, but for now the easiest
way to either reduce the RAM usage (at the risk of slowing things down)
is to set the almost-undocumented ``SYNAPSE_CACHE_FACTOR`` environment
variable. Roughly speaking, a SYNAPSE_CACHE_FACTOR of 1.0 will max out
at around 3-4GB of resident memory - this is what we currently run the
matrix.org on. The default setting is currently 0.1, which is probably
around a ~700MB footprint. You can dial it down further to 0.02 if
desired, which targets roughly ~512MB. Conversely you can dial it up if
you need performance for lots of users and have a box with a lot of RAM.