david@xxxxxxx writes: > > on some kernel versions you are correct about needing swap > ram, but on current > versions you are not. the swap space gets allocated as needed, and re-used as > needed (I don't know the mechanism of this, but I remember the last time this > changed from vm=max(ram,swap) to vm=ram+swap) I don't think I can recall a linux kernel that required swap > ram. However for serious swapping under linux having swap > ram was very useful and pretty much a requirement for a workload that involved swapping heavily (not thrashing). >> I have not heard of many people swapping and not thrashing lately. >> I think part of the problem is that we do random access to the swap >> partition which makes us seek limited. And since the number of >> seeks per unit time has been increasing at a linear or slower rate >> that if we are doing random disk I/O then the amount we can use >> the disk for is very limited. I wonder if we could figure out >> how to push and pull 1M or bigger chunks into and out of swap? > > it has been noted by many people that linux is very slow to pull things back > into ram from swap, significantly slower then simple seed limiting would seem to > account for. Yes. It may be the large amount of random access (my current guess) or it may be something else. I'm wonder if I should build an application with a configurable data set and working set that can be used for swap testing. I don't think it would be very hard and it might help sort through some of the swap performance problems. Eric - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
