logs drop in fluentd when cpu utilisation crossed 1 core

Question

I've noticed log drops occurring when the Fluentd agent pod utilisation exceeds 1 core. Could anyone kindly provide suggestions on how to implement multi-threading to address this log drop issue? Thanks in advance

fluentd_config:

<source>
 @type tail
 @id in_tail_container_logs
 path /var/log/containers/*app*.log
 pos_file /var/log/fluentd-containers.log.pos
 tag k8s.*
 read_from_head true
 <parse>
   @type json
   time_key @timestamp
   time_format %Y-%m-%dT%H:%M:%S.%N%z
   keep_time_key true
 </parse>
</source>

<match k8s.**>
  @type copy
  @id k8s
  <store>
    @type elasticsearch
    @id k8s_es
    @log_level debug
    scheme http
    host  "es.app.host"
    port  "80"
    log_es_400_reason true
    logstash_dateformat %Y.%m.%d.%p
    logstash_format true
    logstash_prefix ${$.kubernetes.labels.app}
    reconnect_on_error true
    reload_on_failure true
    reload_connections false
    suppress_type_name true
    sniffer_class_name Fluent::Plugin::ElasticsearchSimpleSniffer
    request_timeout 2147483648
    compression_level best_compression
    include_timestamp true
    utc_index false
    time_key_format "%Y-%m-%dT%H:%M:%S.%N%z"
    time_key time
    id_key _hash
    remove_keys _hash
    <buffer tag, $.kubernetes.labels.app>
      @type file
      flush_mode interval
      flush_thread_count 16
      path /var/log/fluentd-buffers/k8s.buffer
      chunk_limit_size 48MB
      queue_limit_length 512
      flush_interval 5s
      overflow_action drop_oldest_chunk
      retry_max_interval 30s
      retry_forever false
      retry_type exponential_backoff
      retry_timeout 1h
      retry_wait 20s
      retry_max_times 30
    </buffer>
  </store>
  <store>
    @type prometheus
    @id k8s_pro
    <metric>
      name fluentd_output_status_num_records_total
      type counter
      desc The total number of outgoing records
      <labels>
        tag ${tag}
        hostname ${hostname}
      </labels>
    </metric>
  </store>

how to use multi threading in fluentd to use more than 1 core and mitigate this issue.