ionice.ml

(*
 * Copyright (C) Citrix Systems Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; version 2.1 only. with the special
 * exception on linking described in file LICENSE.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *)

open Stringext
open Xenops_interface.Vbd

(* ionice invocations apply a 'class' and a 'parameter' to a process *)
let to_class_param =
	let to_param = function
		| Highest -> 0
		| High    -> 2
		| Normal  -> 4
		| Low     -> 6
		| Lowest  -> 7
		| Other x -> x in
	function
		| RealTime x   -> 1, (to_param x)
		| Idle         -> 3, (to_param Lowest)
		| BestEffort x -> 2, (to_param x)

let of_class_param_exn cls param =
	let param = match param with
		| "7" -> Lowest
		| "6" -> Low
		| "4" -> Normal
		| "2" -> High
		| "0" -> Highest
		| x -> Other (int_of_string x) in
	match cls with
		| "idle"
		| "3" -> Idle
		| "realtime"
		| "1" -> RealTime param
		| "best-effort"
		| "2" -> BestEffort param
		| _ -> raise Not_found (* caught below *)

exception Parse_failed of string

let parse_result_exn s : qos_scheduler option =
	try
		match String.split ' ' (String.strip String.isspace s) with
			| [ cls_colon; "prio"; param ] ->
				let cls = String.sub cls_colon 0 (String.length cls_colon - 1) in
				Some (of_class_param_exn cls param)
			| _ ->
				raise (Parse_failed s)
	with _ ->
		raise (Parse_failed s)

let set_args qos pid =
	let cls, param = to_class_param qos in
	[
		Printf.sprintf "-c%d" cls;
		Printf.sprintf "-n%d" param;
		Printf.sprintf "-p%d" pid
	]

let get_args pid = [ Printf.sprintf "-p%d" pid ]