Re: swapout frenzy solution

[Rik van Riel <H.H.vanRiel@fys.ruu.nl>]

On Thu, 5 Mar 1998, Rik van Riel wrote:

> I've just come up with a simple 'solution' for the swapout
> frenzy experienced by the recent free_memory_available()
> test in kswapd.

Hate to follow up to my own posts, but here it goes:
Once my system reached a state where it needed to
free a _large_ (MAX_ORDER) area, nr_free_pages kept
lingering around free_pages_high * 4 :-(
This means that this scheme doesn't really work...

Then I've got another possible solution. In try_to_swap_out,
we:
- test what page-order this page is holding up
- change the following:
  if (page->age)
- into:
  if (page->age - order_block(page))

This means that a page blocking an order-5 area will
be heavily penalized for this, so this page will be
freed earlier than other pages (which don't occupy
'critical' regions.

Of course, reserving 1/16th of memory for exclusive
use by the page and buffer cache (which we can already
clean on a page-by-page basis) will be far superior
to this...

I don't have time to code this up before the weekend,
so you've got all the time to decide which solution
you'd like to see implemented...

Rik.
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