Default filtercache

Each nodes elasticsearch.yml does not have any rule for filter-cache, still during load testing we found spikes in filter-cache, so is ES sets some default 10% (ES docs says default is 10%, so assume that that default setting must be in Elasticsearch.yml file but it was not there, or we must have removed it) as a filter cache size, even though it's not in our ES *.yml file?

There are some settings like that we set even without them being in the config file.