On Thu, Apr 28, 2011 at 03:31:55PM +0200, Pavel Machek wrote:

Hi!

quoted

For testing swap-over-NBD, a machine was booted with 2G of RAM with a
swapfile backed by NBD. 16*NUM_CPU processes were started that create
anonymous memory mappings and read them linearly in a loop. The total
size of the mappings were 4*PHYSICAL_MEMORY to use swap heavily under
memory pressure. Without the patches, the machine locks up within
minutes and runs to completion with them applied.

Comments?

Nice!

It  is easy to see why swapping needs these fixes, but... dirty memory
writeout is used for memory clearing, too. Are same changes neccessary
to make that safe?

Dirty page limiting covers the MAP_SHARED cases and are already
throttled approprately.

(Perhaps raise 'max dirty %' for testing?)

Stress testing passed for dirty ratios of 40% at least. Maybe it would
cause issues when raised to nearly 100% but I don't think that is a
particularly interesting use case.

-- 
Mel Gorman
SUSE Labs

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