From 9b93a2238901231006ccd888446cd8eb13229a50 Mon Sep 17 00:00:00 2001 From: Jakob Unterwurzacher Date: Sat, 27 Dec 2008 22:39:10 +0100 Subject: ionice: Extend the man page to explain the "none" class and cpu-nice inheritance Extend the ionice man page to explain the "none" class and how the cpu-nice => io-priority inheritance works. Signed-off-by: Jakob Unterwurzacher --- schedutils/ionice.1 | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'schedutils/ionice.1') diff --git a/schedutils/ionice.1 b/schedutils/ionice.1 index 2eca2b8b1..aef40c38e 100644 --- a/schedutils/ionice.1 +++ b/schedutils/ionice.1 @@ -11,7 +11,7 @@ This program sets or gets the io scheduling class and priority for a program. If no arguments or just \fI-p\fR is given, \fIionice\fR will query the current io scheduling class and priority for that process. -As of this writing, Linux supports 3 scheduling classes: +As of this writing, a process can be in one of four scheduling classes: .IP "\fBIdle\fP" A program running with idle io priority will only get disk time when no other @@ -21,9 +21,9 @@ class does not take a priority argument. Presently, this scheduling class is permitted for an ordinary user (since kernel 2.6.25). .IP "\fBBest effort\fP" -This is the default scheduling class for any process that hasn't asked for -a specific io priority. Programs inherit the CPU nice setting for io -priorities. This class takes a priority argument from \fI0-7\fR, with lower +This is the effective scheduling class for any process that hasn't asked for +a specific io priority. +This class takes a priority argument from \fI0-7\fR, with lower number being higher priority. Programs running at the same best effort priority are served in a round-robin fashion. @@ -35,6 +35,14 @@ some care, as it can starve other processes. As with the best effort class, will receive on each scheduling window. This scheduling class is not permitted for an ordinary (i.e., non-root) user. +.IP "\fBNone\fP" +A process that that hasn't asked for a specific io priority will formally be +in this class. The io scheduler will treat a process that is in this class as +if it were in the best effort class. The priority within the best effort +class will be dynamically derived from the cpu nice level of the process: +io_priority = (cpu_nice + 20) / 5 + + .SH OPTIONS .IP "\fB-c \fIclass\fP" The scheduling class. \fI1\fR for real time, \fI2\fR for best-effort, \fI3\fR for idle. -- cgit v1.2.3-55-g7522