Messages in this thread | | | From | "Buddy Lumpkin" <> | Subject | RE: why swap at all? | Date | Wed, 26 May 2004 04:46:53 -0700 |
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>> >> That's true, but it's not a magical property of swap space >> - extra physical >> RAM would do more or less the same thing. >>
> Well it is a magical property of swap space, because extra RAM > doesn't allow you to replace unused memory with often used memory.
> The theory holds true no matter how much RAM you have. Swap can > improve performance. It can be trivially demonstrated.
I bet you have demonstrated this. It strikes me of an observation that could be made in a lab environment. But your failing to realize that:
1) you will fill physical memory with pages eventually or your not doing work.
2) pages do not just silently move to the swap device. They move as a result of a memory shortfall
3) once physical memory is full, file system I/O will only benefit from reads that incur a minor fault. All other file system operations are bound by the rate you can reclaim pages from physical memory.
4) non-filesystem backed pages are still effected the same way, nothing has changed. When you run your next filesystem related operation, those pages will be faulted into physical memory, and something will be evicted to it's backing store (remember, memory is full).
--Buddy
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