That's because, when swap space is exhausted, Linux can't
make good use of the don't-swap-if-clean-and-already-swapped
strategy anymore.
When you've got plenty of swap space, and a clean page is
to be swapped out, it can be just forgotten about when it's
already written to swap. When however that clean page was
just purged from swap to accomodate another program, it will
have to be rewritten, thereby doubling the amount of disk
I/O needed :-(
Just make sure you have enough swap, and performance
should rock...
Rik.
+-----------------------------+------------------------------+
| For Linux mm-patches, go to | "I'm busy managing memory.." |
| my homepage (via LinuxHQ). | H.H.vanRiel@fys.ruu.nl |
| ...submissions welcome... | http://www.fys.ruu.nl/~riel/ |
+-----------------------------+------------------------------+
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