borrow percentages & new VM scheme

borrow percentages & new VM scheme

[Rik van Riel]

Hi,

I've found that the rediculous amount of swapping associated
with 2.1.130-pre3 goes away if you reduce the borrow percentages
for both buffer and page cache to 10 percent...

We probably want 15% for the borrow percentage on small (<32M)
boxes, but nothing more either.

Lowering the borrow percentage gives kswapd the 'need' to prune
the cache once in a while, even when it is still easy to unmap
something in swap_out().

Because kswapd usually only switches when there is a failure
for either swap_out() or shrink_mmap() it can continue with
swap_out() (since there still is not enough memory free) doing
1000+ swapouts a second for a 7 second period (on my box) which
is just a bit too much.

We need some sort of mechanism to make kswapd switch tactics
more often, or else system stability and performance may
suffer.

regards,

Rik -- now completely used to dvorak kbd layout...
+-------------------------------------------------------------------+
| Linux memory management tour guide.        H.H.vanRiel@phys.uu.nl |
| Scouting Vries cubscout leader.      http://www.phys.uu.nl/~riel/ |
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