On Mon, Sep 06, 2004 at 02:11:29PM -0500, Ray Bryant wrote:

What is unexpected is that the amount of swap space used at a particular
swappiness setting varies dramatically with the kernel version being 
tested, in spite of the fact that the basic swap_tendency calculation in 
refile_ianctive_zone() is unchanged.  (Other, subtle changes in the vm as a 
whole and this routine in particular clearly effect the impact of that 
computation.)
For example, at a swappiness value of 0, Kernel 2.6.5 swapped out 0 bytes,
whereas Kernel 2.6.9-rc1-mm3 swapped out 10 GB.  Similarly, most kernels
have a significant change in behavior for swappiness values near 100, but
for SLES9 the change point occurs at swappness=60.
A scan of the change logs for swappiness related changes shows nothing that 
might explain these changes.  My question is:  "Is this change in behavior
deliberate, or just a side effect of other changes that were made in the 
vm?" and "What kind of swappiness behavior might I expect to find in future 
kernels?".

IIRC no deliberate /proc/sys/vm/swappiness semantic changes were merged.
The policy tweakers have something to answer for here unless some stats
they rely upon have since been flubbed. Logging periodic snapshots of
/proc/vmstat for these benchmarks may be helpful to implicate specific
statistics' bungling or rule out statistic miscalculation as causes.


-- wli
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>