Re: [PATCH] make blkfront/blktagp2 respect the elevator=xyz command line option

[Paolo Bonzini <pbonzini@redhat.com>]

>> For blkfront, I agree. Is there a use case for defaulting to something
>> different than a system default?
>
> Noone else does it, except maybe some old s390 drivers. We'll kill it then.

The rationale was that guest I/O delays depend on the I/O done by all 
other guests at the same time.  So, in theory there is no need to 
schedule it on the guest---assuming hypercalls are fast enough it should 
be passed down to the host immediately and left to be scheduled together 
with all the other host I/O.

However, actual benchmarks show that this does not always hold 
(sometimes disastrously) so killing the elevator_init call is safe and 
is fine by me.

Paolo