Mikkel L. Ellertson wrote:
James Kosin wrote:Having TOO much swap space can be a detriment and not an asset. Usually, the rule of thumb I go by is allocate about 2x the amount of physical memory installed on the system; for machines with < 1M. This number will need to approach more or less 1x for machines with 1-2M. With machines with > 2M; I'm not sure swap space will make much of a difference, unless you rely on X heavily.I have never head of a problem of having too much swap space. What kind of problems does it cause? I know you get system slowdown if you are doing too much swapping, but that is a different problem from having too much swap space.JamesMikkel
Ok,(1) The operating system has to manage the swap space like it manages memory space and allocation. The swap space is a big area that has to be divided up just like the RAM. The OS uses what is commonly called a page table to accomplish this. (2) As the memory and or swap space gets used and divided up with the applications this page table gets larger and larger (don't worry, there is a limit).
Here is were it takes some understanding, I'm lacking at the moment. To keep track of everything we have a single page table and a bit determines if we are talking about physical memory or swap memory. In the OS; everything (or almost so) uses this page table to look up virtual addresses and maps them to physical addresses. If the address is in swap space then a disk access is needed to get to the data; weather it pages the application back to physical RAM at this point is really up to the OS, some do and some don't. This page table has to reside in PHYSICAL RAM somewhere usually to keep the access time down to a reasonable level. If the page table grows too large you get issues with the table and lookup issues.
James
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