Re: Odd swap behavior

[Rajagopal Ananthanarayanan <ananth@sgi.com>]

Rik van Riel wrote:

> > Does that mean stack pages of processes are not included?
> > Non-aggressive swap can hurt performance.
> 
> I don't really see a clean way to do that in 2.4 ...

We can perhaps talk about this at the Storage Workshop ...

	[ ... ]

> > Would it not be more efficient to bung clean (read) pages directly
> > to inactive_clean on age = 0?
> 
> I don't know if this would make any difference...

I think it would. Consider steady state where pages
are all "in use". Any new allocation has to start with
pushing a page from active -> inactive, and then
inactive -> inactive_clean, if necessary, and then reclaim.
Now,  if we had pages which _are_ clean, then the path taken
is simply active -> inactive_clean -> reclaim.


> 
> And in fact, I'm contemplating adding /all/ pages
> that are deactivated to the inactive_dirty list,
> since that way we'll reclaim all inactive pages
> in FIFO order.
> 
> Currently we may "skip" some pages that were put
> on the inactive_dirty list but were cleaned up
> subsequently because we can find enough active
> pages that can be moved to the inactive_clean
> list immediately ...
> 

This is an interesting idea, although it seems
antithetical to what I said above. I think pure
FIFO has its merits in accomodating longer locality of
reference; it can help dbench.

If you have a patch (to always deactivate to inactive_dirty),
I can help you gauge it with the benchmarks ...

 
--------------------------------------------------------------------------
Rajagopal Ananthanarayanan ("ananth")
Member Technical Staff, SGI.
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