What is Virtual Memory and why is it so high? (Mac)

What is Virtual Memory and why is it so high? (Mac)
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answer:Virtual memory is an abstraction that decouples memory used by programs from the physical hardware. Basically it makes it possible for a computer without enough RAM to still run all the programs a user might run simultaneously. How it works is the program is given a block of virtual memory that may sound obscenely large and the program may or may not use all of that memory. What happens is if there isn’t enough physical RAM available the operating system will swap out some of the data currently unused that is stored in RAM and copy it to the disk. This is called paging (data is stored in pages in RAM). Page ins aren’t a big deal but page outs are—page outs means you don’t have enough RAM for all the programs you’re currently running so it had to write out some pages to disk in order to make room for another program. When the other program goes to use a page that’s been written to disk it has to go and get that page and then that page is brought back into memory. Sometimes this can lead to “thrashing” where the same pages and written in and out over and over. That would definitely make things slow. You have three real options:     1. Run fewer programs     2. Buy more RAM     3. Get a faster disk so page outs are fast (i.e. get a solid-state drive) I’d recommend all three options (in combination). Just for reference memory is a few orders of magnitude faster than disk drives so more RAM (or minimizing your usage of RAM) can make a huge difference. Summary: huge virtual memory numbers aren’t a problem at all but paging to disk is an issue.
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