From mboxrd@z Thu Jan 1 00:00:00 1970 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 Message-ID: <20040906224830.GI3106@holomorphy.com> References: <413CB661.6030303@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <413CB661.6030303@sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Ray Bryant Cc: Andrew Morton , Kernel Mailing List , linux-mm@kvack.org, Rik van Riel , Nick Piggin , Con Kolivas List-ID: 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: aart@kvack.org