in_tail: Add option file_cache_advise

pipeline/inputs/tail.md

@@ -34,7 +34,7 @@ The plugin supports the following configuration parameters:
 | Tag | Set a tag \(with regex-extract fields\) that will be placed on lines read. E.g. `kube.<namespace_name>.<pod_name>.<container_name>`. Note that "tag expansion" is supported: if the tag includes an asterisk \(\*\), that asterisk will be replaced with the absolute path of the monitored file \(also see [Workflow of Tail + Kubernetes Filter](../filters/kubernetes.md#workflow-of-tail-kubernetes-filter)\).                                                                                       |  |
 | Tag\_Regex | Set a regex to extract fields from the file name. E.g. `(?<pod_name>[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-`                                                                                                                                                                                                                                                                                                                    |  |
 | Static\_Batch\_Size | Set the maximum number of bytes to process per iteration for the monitored static files (files that already exists upon Fluent Bit start).                                                                                                                                                                                                                                                                                                                                                               | 50M     |
-
+| File\_Cache\_Advise | Set the posix_fadvise in POSIX_FADV_DONTNEED mode. This will reduce the usage of the kernel file cache. This option is ignored if not running on Linux.                                                                                                                                                                                                                                                                                                                                                              | On     |
 
 Note that if the database parameter `DB` is **not** specified, by default the plugin will start reading each target file from the beginning. This also might cause some unwanted behavior, for example when a line is bigger that `Buffer_Chunk_Size` and `Skip_Long_Lines` is not turned on, the file will be read from the beginning of each `Refresh_Interval` until the file is rotated.