From 9bc0e24612e709449e3ff6fea926dd2ae746dfca Mon Sep 17 00:00:00 2001 From: Karel Zak Date: Thu, 22 Jan 2009 12:54:06 +0100 Subject: ionice: a little cleanup of "none" description We practically have three io scheduling classes. The "none" is de facto "best-effort" class for processes that has not asked for io priority. Signed-off-by: Karel Zak --- schedutils/ionice.1 | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) (limited to 'schedutils/ionice.1') diff --git a/schedutils/ionice.1 b/schedutils/ionice.1 index aef40c38e..7f410c6f1 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, a process can be in one of four scheduling classes: +As of this writing, a process can be in one of three scheduling classes: .IP "\fBIdle\fP" A program running with idle io priority will only get disk time when no other @@ -21,12 +21,18 @@ 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 effective scheduling class for any process that hasn't asked for +This is the effective scheduling class for any process that has not 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. +The processes that has not asked for io priority formally use "\fBnone\fP" as a +scheduling class, but the io scheduler will treat such processes as if they +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. + .IP "\fBReal time\fP" The RT scheduling class is given first access to the disk, regardless of what else is going on in the system. Thus the RT class needs to be used with @@ -35,14 +41,6 @@ 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