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Re: [Xen-users] Xen hard-disk performance regression?

Le lundi 12 avril 2010 à 20:56 +0200, Fabiano Francesconi a écrit :
> Ok the problem seems solved.
> An ##xen irc user, jamon, told me to add 'elevator=noop' as kernel
> bootflag in order to disable I/O scheduler on the domU.
> This is quite interesting since, as he states "getting different guests
> all trying to read/write at the same time with different schedulers, or
> even different kernels (linux cf. windows cf. bsd etc.) isn't as good as
> letting the host do all the heavy lifting and not have to worry about
> different write caches, flushing etc. that different guests might be doing.
> Actually I was wondering about my situation. My whole disk is passed
> entirely to the domU so this shouldn't be a problem at all.
> After rebooting the machine what I get is:
> real  0m16.993s
> user  0m0.009s
> sys   0m1.143s

much work was done on IO on the last kernel versions, and the most
recent ones are speedier than older, but some things changed (for
example the "Anticipatory scheduler" is gone away in .33) and some
tweaking has to be done.



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