elasticsearch 索引越多越吃内存，还没法gc

elasticsearch 大概1000个索引，吃内存800m,而且还没法gc, es的索引是按照logstash建议的设置全局的mapping，后面索引越多，内存吃得越多，如何解决呢？
全局mapping部分内容如下：
"logstash": {"order": 0,
"template": "logstash-*",
"settings": {

"index": {

"refresh_interval": "5s"

}

},
"mappings": {

"_default_": {

"dynamic_templates": [

{

"message_field": {

"mapping": {

"fielddata": {

"format": "disabled"

},
"index": "analyzed",
"omit_norms": true,
"type": "string"

},
"match_mapping_type": "string",
"match": "message"

}

}
,
{

"string_fields": {

"mapping": {

"fielddata": {

"format": "disabled"

},
"index": "analyzed",
"omit_norms": true,
"type": "string",
"fields": {

"raw": {

"ignore_above": 256,
"index": "not_analyzed",
"type": "string",
"doc_values": true

}

}

},
"match_mapping_type": "string",
"match": "*"

}

}