On Thursday, July 21 at 18:29 (-0700), Grant said:
> Then why not have a really big swap file? If swap is useful as a > second layer of caching behind RAM, why doesn't everyone with some > extra hard drive space have a 100GB swap file? > You've not understood what I said, I think. Swap is not useful as filesystem cache. Swap is as efficient (probably a little less) than the files on the disk. It's RAM that's efficient as filesystem cache. Where swap comes in is the kernel can swap out pages from "stale" processes, and reclaim the RAM as filesystem cache. Think of it this way: You have a house with an attic. Now the attic is not as "efficient" as say, the middle of your living room. You have a Christmas tree, but you only use that Christmas tree maybe once a year. Now it's much more efficient to keep that Christmas tree in the attic for 11 months of the year and use that reclaimed space in your living room for.. say a coffee table. Then, when you need that Christmas tree in December, you pull it out of the attic and maybe put the coffee table up in the attic for a month. The Christmas tree represents a process that's just sitting out there doing not much half the time, but taking up space. The space in your living room is RAM, and the space in your attic is swap. The coffee table is filesystem cache.
