From: Jason McMullan <jmcmullan@linuxcare.com> To: linux-kernel@vger.kernel.org Subject: What are the VM motivations?? Date: Thu, 21 Jun 2001 19:01:03 -0400 <rant> I've been reading the VM thread off-and-on for, oh, the last 8 _years_ on linux-kernel. It doesn't seem that much progress gets made in any one direction. For every throughput optimination for servers, the desktop people yell 'interactivity'. For every 'long-disk-idle' desire the laptop guys have, others want large buffer caches. It goes back and forth. Everybody pulling from all sides, and the VM performance has stayed (mostly) in the center. Well, I have an idea. Let's take a page from the Neural Network guys (not the code, just the ideas), and look at VM from a motivational perspective. What if the VM were your little Tuxigachi. A little critter that lived in your computer, handling all the memory, swap, and cache management. What would be the positive and negative feedback you'd give him to tell him how well he's doing VM? Here's a short, off-the-cuff list that hopefully most everyone can agree on. Positive -------- * Low system CPU load for the VM timeslice * Process IO requests / Disk IO is less than 1.0 * Large idle times between disk activity * Process don't have to wait long for pages from VM. * etc. Negative -------- * High CPU usage for VM * High disk IO for low number of process IO requests. * Disk is rarely idle * Processes stall for a long time waiting for VM. * Deadlocks (fatal!) * etc. One we know how we would 'train' our little VM critter, we will know how to measure its performance. Once we have measures, we can have good benchmarks. Once we have good benchmarks - we can pick a good VM alg. Or heck, let's just make the VM a _real_ Neural Network, that self trains itself to the load you put on the system. Hideously complex and evil? Well, why not wire up that roach on the floor, eating that stale cheese doodle. It can't do any worse job on VM that some of the VM patches I've seen... </rant> -- Jason McMullan, Senior Linux Consultant Linuxcare, Inc. 412.432.6457 tel, 412.656.3519 cell jmcmullan@linuxcare.com, http://www.linuxcare.com/ Linuxcare. Putting open source to work. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/