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Date: Tue, 19 Jun 2012 10:11:26 +0800 From: "gnehzuil.lzheng@...il.com" <gnehzuil.lzheng@...il.com> To: Jens Axboe <axboe@...nel.dk> CC: Rob Landley <rob@...dley.net>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, util-linux@...r.kernel.org Subject: Re: Why does ionice(1) ban the user to set back to 'none' class? [CC'd to util-linux mailing list] On 06/18/2012 09:28 PM, Jens Axboe wrote: > 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. > Thanks for your reply. Hopefully we can get some feedbacks from util-linux crew. Regards, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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