Re: scheduler question 2.6.16.x

[Andre Tomt <andre@tomt.net>]

Nick Warne wrote:
> On Tuesday 25 April 2006 19:15, Jens Axboe wrote:
> 
>>> But I can build both in... so I guess then the kernel decides what is
>>> the best to use?  Or should it be so I am only allowed to select one
>>> or the other and allowing both is an oversight?
>> See the option no more than two lines down from that, default io
>> scheduler. Also see Documentation/block/switching-sched.txt and/or
>> Documentation/kernel-parameters.txt (elevator=) section.
> 
> Hi Jens,
> 
> I haven't got the switching-sched.txt, although I found a sched-design.txt... 
> but what I meant was if I select whatever default, do/can I still need to 
> select either/or scheduler?
> 
> i.e. why doesn't 'default selection option' only allow that scheduler to be 
> selected?

That would be a artificial (and silly!) limit - the io-scheduler is 
pluggable and selectable at boot, you can even change it at run time at 
a per block device level.

See the elevator= boot option and /sys/block/<device>/queue/scheduler