Messages in this thread | | | Date | Mon, 6 Sep 2004 15:48:30 -0700 | From | William Lee Irwin III <> | Subject | Re: swapping and the value of /proc/sys/vm/swappiness |
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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.
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