On Wed, 19 Jul 2006 10:18:44 BST, Ian Stirling said: > To paraphrase shakespear - all the world is not a P4 - and all the swap > devices are not hard disks. Been there, done that. I used to admin a net of Sun 3/50s where /dev/swap was a symlink to a file on an NFS server, because the "shoebox" local hard drives for those were so slow that throwing it across the ethernet to a 3/280 with Fujitsu Super-Eagles was faster... > For example - I've got a 486/33 laptop with 12M RAM that I sometimes use > , with swapping to a 128M PCMCIA RAM card that I got from somewhere. If we go to the effort of writing code that tries to be smart about grouping swap reads/writes by cost, it's easy enough to flag any sort of ram-disk device as a 'zero seek time' device. Remember that I suggested making it dependent on "how long until the next pass of the elevator" - for a ramdisk that basically is zero, so the algorithm easily degenerates into "just queue the requests in expected order you'll need the results". > 20K instructions wasted on a device with no seek time is just annoying. On the other hand, how long does it take to move a 4K page across the PCMCIA interface? If you're seeing deep queues on it, you may *still* want to optimize the order of requests...
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