Messages in this thread | | | Date | Tue, 7 Aug 2007 23:35:27 +0200 | From | dragoran <> | Subject | Re: allow non root users to set io priority "idle" ? |
| |
so there is no real reason not to allow it for non root users? removing the check is easy (3 lines) .... or are there any other issues/problems?
On 8/7/07, Jens Axboe <jens.axboe@oracle.com> wrote: > On Mon, Aug 06 2007, Andi Kleen wrote: > > > couldn't this be fixed by bumping idle tasks to middle while they hold a > > > > Usually to high. > > > > But it's all complicated and hasn't been done consistently > > (there are real time mutexes in the -rt kernel for example, > > but there are lots of other locks and they have higher overhead too) > > and it's unclear we really want to do all this complexity anyways. > > > > Also as I said the problem could then still happen in user space > > which then would all need to be fixed to handle PI too. > > > > In some cases the relationship is also not as simple as a single > > lock. And for IO handling it would be likely quite hard. > > > > I personally always found idle priorities quite dubious because > > even if they worked reliable for the CPU they will clear your cache/ > > load your memory controller and impact all other programs because > > of this. And for the disk they will cause additional seeks which are > > also very costly. > > But that is why the idle priority implementation in CFQ adds a grace > period before idle prio tasks are run. So that concern should not be an > issue, if so the grace period needs to be enlarged. That at least covers > the seek side of things. If idle io tasks run, then the IO load on the > system must be very low to zero. Hence other IO relevant resource > contention isn't an iissue. > > -- > Jens Axboe > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |