I think the TSM example is what is showing the strength of the architecture.
Every computer load (mix of programs used for your application) have a different need for memory. My first home UNIX system was a non-virtual memory system, so EVERYTHING stayed in memory, and on a 386 with under 1G ram was 'interesting'. Once virtual memory was being used we 'paged'. Read/wrote one page at a time. Shortly after we started using swapping to take a 'set of pages', normally defined by a 'reasonable buffer' for the underlying device. This was especially true a devices were addressed by cylinder/track/sector addressing. When the linear addressing of devices (a good thing) obfuscated the hardware using onboard micro controllers, and the underlying architecture of the drives were obfuscated further, add in larger on-device buffers that can help buffer reads and sometimes writes, the optimization for device became harder and less needed than before. Now we basically do no paging, and only swap. Memory sizes have exploded (Thank you Dr. Moore!), we don't concern ourselves with memory conservation, writing programs that keep loops into a few pages, rather than touching lots of pages of memory, designing data structures for high information density encoding, etc. Oh well. In summary, given the current state of machines: 1. what we have works pretty well overall, without much tweaking. 2. reducing swap rate is a good thing 3. normally some swap use means you are getting use of all your memory (as cache, buffers, or program memory, still being used) 4. one of the easiest and cheapest upgrades to most systems (unless you hit architectural limits) is to add more memory. 5. active use of swap on a continuing basis, should be reduced for long term system health 6. there are some fairly easy kernel tuning procedures to determine the handling of swap ( http://en.wikipedia.org/wiki/Swappiness and other searches for swappiness and related items ), and various issues. It just takes research. No one knob tunes everything. This is NOT an exact science. There are more variables involved than most of us can handle in our heads. The idea is to get your system to do what you want with minimal overhead (and in my case, minimal extra effort). I have my swappiness set to 45 on my laptop, but I didn't see a HUGE change, but it is supposed to be a little better for interactive use. Higher numbers are better for typical file server use, where more buffer space normally helps. Enjoy... _______________________________________________ Tech mailing list Tech@lists.lopsa.org https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
