LDP
/
man-pages
mirror of https://github.com/mkerrisk/man-pages
0
1
Fork 0
Code Releases Activity

ioprio_set.2: Document meaning of ioprio==0 

Reported-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-05-11 10:09:05 +02:00
parent a311ffd05b
commit 02906043a4
1 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
man2/ioprio_set.2
View File

@ -137,7 +137,10 @@ value), this macro returns its priority
component.
.PP
See the NOTES section for more
information on scheduling classes and priorities.
information on scheduling classes and priorities,
as well as the meaning of specifying
.I ioprio
as 0.
I/O priorities are supported for reads and for synchronous
.RB ( O_DIRECT ,
@ -222,6 +225,19 @@ These system calls have an effect only when used
in conjunction with an I/O scheduler that supports I/O priorities.
As at kernel 2.6.17 the only such scheduler is the Completely Fair Queuing
(CFQ) I/O scheduler.
If no I/O scheduler has been set for a thread,
then by default the I/O priority will follow the CPU nice value
.RB ( setpriority (2)).
In Linux kernels before version 2.6.24,
once an I/O priority had been set using
.BR ioprio_set (),
there was no way to reset the I/O scheduling behavior to the default.
Since Linux 2.6.24,
.\" commit 8ec680e4c3ec818efd1652f15199ed1c216ab550
specifying
.I ioprio
as 0 can be used to reset to the default I/O scheduling behavior.
.SS Selecting an I/O scheduler
I/O schedulers are selected on a per-device basis via the special
file