Messages in this thread | | | Date | Mon, 18 Jun 2012 15:28:48 +0200 | From | Jens Axboe <> | Subject | Re: Why does ionice(1) ban the user to set back to 'none' class? |
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On 06/18/2012 01:48 PM, Zheng Liu wrote: > Hi Jens, > > I meet a problem when I use ionice(1) to adjust a process's io priority. > I do the following operations: > > $ ionice -p${pid} > none: prio 0 > $ ionice -p${pid} -c2 -n4 > $ ionice -p${pid} > best-effort: prio 4 > $ ionice -p${pid} -c0 -n0 > $ ionice -p${pid} > best-effort: prio 0 > > So I cannot set scheduling class back to 'none'. If I call ioprio_set(2) > directly, it will be fine. But if I use ionice(1), I cannot change it. I > read the docs about ionice in [1]. I notice this code: > > switch (ioprio_class) { > case IOPRIO_CLASS_NONE: > ioprio_class = IOPRIO_CLASS_BE; > ^^^^^^^^^^^^^^^^ > *It means that we cannot set back to none.* > break; > case IOPRIO_CLASS_RT: > case IOPRIO_CLASS_BE: > break; > case IOPRIO_CLASS_IDLE: > ioprio = 7; > break; > default: > printf("bad prio class %d\n", ioprio_class); > return 1; > } > > My question is why we need to ban the user to set back to 'none'. Is there > some reasons? Thank you.
The kernel code does allow it, so it's only in the tool that this restriction exists. I don't think we have a particularly good reason to have it there. This is a tools question, though, not a kernel issue. I suggest you take it up with the util-linux crew. I'm fine with removing this restriction from ionice, especially since you could just roll your own that did it.
-- Jens Axboe
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