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

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

> > 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

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