Re: [OFFTOPIC] UltraSparc MMU problems

Hendrik Visage (hendrik@sdn.co.za)
Tue, 27 Oct 1998 13:27:02 +0200


David S. Miller wrote:

> Date: Tue, 27 Oct 1998 21:35:16 +1100
> From: Richard Gooch <rgooch@atnf.csiro.au>
>
> David S. Miller writes:
> > Solaris's TLB miss strategy is pretty hopeless...
>
> What does the OS have to do with it? Once the TLB's are set up, why
> does the OS need to intervene?
>
> If the OS uses a stupid scheme to replace a missing TLB entry and uses
> inefficient tables as backing store for mappings, it will thrash the
> L2 cache.
>
> Note that Solaris and some other svr4 folks swap page tables out to
> disk when memory is tight... when they get tapped back in you might
> not get the nice cache patterns you had before...

Note: Richard said it got FASTER after the pageout-pagein operation!!
Thus, you now have a more efficient set etc. than before!!!

The only thing I think of that would make it FASTER (after the
pageout/pagein), is that Soalris only page back the needed pages, as needed,
and thus could be more optimized than before... ie. the spread across memory
could be less than before the pageout/pagein.

Richard, do try the following (And tell us the results please):
Repeat your operation as before, but after that:
- reload the dataset from disk etc. (Thus clearing out the current in memory
copy with a fresh copy)
- re-render and time

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