Re: [RFC/RFT 0/6] nommu: improve the vma list handling

[Greg Ungerer]

On 29/03/11 08:01, Andrew Morton wrote:
> On Mon, 28 Mar 2011 22:56:41 +0900
> Namhyung Kim<namhyung@xxxxxxxxx>  wrote:
>
> > When I was reading nommu code, I found that it handles the vma list/tree in
> > an unusual way. IIUC, because there can be more than one identical/overrapped
> > vmas in the list/tree, it sorts the tree more strictly and does a linear
> > search on the tree. But it doesn't applied to the list (i.e. the list could
> > be constructed in a different order than the tree so that we can't use the
> > list when finding the first vma in that order).
> >
> > Since inserting/sorting a vma in the tree and link is done at the same time,
> > we can easily construct both of them in the same order. And linear searching
> > on the tree could be more costly than doing it on the list, it can be
> > converted to use the list.
> >
> > Also, after the commit 297c5eee3724 ("mm: make the vma list be doubly linked")
> > made the list be doubly linked, there were a couple of code need to be fixed
> > to construct the list properly.
> >
> > Patch 1/6 is a preparation. It maintains the list sorted same as the tree and
> > construct doubly-linked list properly. Patch 2/6 is a simple optimization for
> > the vma deletion. Patch 3/6 and 4/6 convert tree traversal to list traversal
> > and the rest are simple fixes and cleanups.
> >
> > Note that I don't have a system to test on, so these are *totally untested*
> > patches. There could be some basic errors in the code. In that case, please
> > kindly let me know. :)
> >
> > Anyway, I just compiled them on my x86_64 desktop using this command:
> >
> >    make mm/nommu.o
> >
> > (Of course this required few of dirty-fixes to proceed)
> >
> > Also note that these are on top of v2.6.38.
> >
> > Any comments are welcome.
>
> That seems like a nice set of changes.  There isn't much I can do with
> them at this tims - hopefully some of the nommu people will be able to
> find time to review and test the patches.

That does seem like a nice set of changes. I have compiled and run
tested on my ColdFire non-mmu targets, and it looks good.

So for the whole series from me that is:

Acked-by: Greg Ungerer <gerg@uclinux>


> (Is there a way in which one can run a nommu kernel on a regular PC?  Under
> an emulator?)

There is some around. Though none I have used I could recommend
off hand. I have used Skyeye for emulating non-mmu ARM on a PC,
but the mainline kernel lacks a serial driver for console on that
(limiting its current usefullnedd quite a bit).

I ran the freely available ColdFire one many years ago, bu I haven't
tried it recently.

Regards
Greg


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Greg Ungerer  --  Principal Engineer        EMAIL:     gerg@xxxxxxxxxxxx
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