Re: [PATCH] MMIO: Make coalesced mmio use a device per zone

[Avi Kivity <avi@redhat.com>]

On 07/19/2011 01:17 PM, Sasha Levin wrote:
> On Tue, 2011-07-19 at 12:59 +0300, Avi Kivity wrote:
> >  On 07/19/2011 12:53 PM, Sasha Levin wrote:
> >  >  >   Make these per-guest instead of global.  The lock may be contended, and
> >  >  >   the list shouldn't hold items from different guests (why is it needed,
> >  >  >   anyway?)
> >  >  >
> >  >
> >  >  We only need the list for removal, since we only have the range we want
> >  >  to remove, and we want to find all devices which contain this range.
> >  >
> >
> >  All devices in the same guest which contain this range.  Your patch
> >  removes devices from all guests.
> >
>
> Yup. I've messed up guest-locality. Will fix.
>
> Also, I found this comment when increasing NR_IOBUS_DEVS:
>
> /*
>   * It would be nice to use something smarter than a linear search, TBD...
>   * Thankfully we dont expect many devices to register (famous last words :),
>   * so until then it will suffice.  At least its abstracted so we can change
>   * in one place.
>   */
>
> Since so far we've registered 5-6 devices, and now it may increase
> significantly (since we may want to do the same change to ioeventfds,
> which work the same way) - how would you feel if we make devices
> register range(s) and do a rbtree lookup instead of a linear search?
>

It makes sense.  In fact your change is a good first step - so far it 
was impossible to to a clever search since the seaching code was not 
aware of the ranges (and could not be, since the single coalesced mmio 
device had multiple ranges).

Rather than an rbtree, I suggest putting all ranges in an array and 
sorting it, then using binary search.

-- 
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