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Use secured virtual memory?
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Mac Elite
Join Date: Jan 2001
Status:
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Anyone know if secured virtual memory is on by default in Leopard? Also, are there any cons of having it on? Is there a big performance hit?
Thanks!
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Mac Elite
Join Date: Mar 2003
Location: Virginia
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It's off by default and is an option in Tiger as well. No performance hit. Why not just try it?
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Senior User
Join Date: Sep 2005
Location: Anson, TX
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I did a fresh install of Leopard and i just checked the security prefpane...it's enabled.
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Administrator  Join Date: May 2000
Location: California
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There is a performance overhead to using secure virtual memory. Memory blocks have to be encrypted before being written to disk, then decrypted when pulled back off disk. If you have a multicore Mac, you may not notice the extra CPU load most of the time, but there's no way around the slight added delays on read/write.
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Addicted to MacNN
Join Date: Jan 2003
Location: ~/
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...and probably not necessary unless you're also using FileVault. Why encrypt the VM if the rest of your machine is wide open and unsecured?
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Mac Elite
Join Date: Mar 2003
Location: Virginia
Status:
Offline
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Originally Posted by reader50 
There is a performance overhead to using secure virtual memory. Memory blocks have to be encrypted before being written to disk, then decrypted when pulled back off disk. If you have a multicore Mac, you may not notice the extra CPU load most of the time, but there's no way around the slight added delays on read/write.
Of course there will be some overhead but it will be imperceptible which is why I said there would be no performance hit.
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Posting Junkie
Join Date: Nov 2000
Location: in front of my Mac
Status:
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OK, can anybody offer hard numbers or even benchmarks for the performance hit due to secure VM? This thread is gonna go nowhere as long as some say "it's negligible" while others say "there will definitely be a performance hit".
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Mac Elite
Join Date: Mar 2003
Location: Virginia
Status:
Offline
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Originally Posted by Simon
OK, can anybody offer hard numbers or even benchmarks for the performance hit due to secure VM? This thread is gonna go nowhere as long as some say "it's negligible" while others say "there will definitely be a performance hit".
Why don't you try it and see for yourself? As for my computer, I cannot notice anything nor can I see any task in Activity Monitor over 1%.
I think the other poster who said there will be a performance hit was the lawyer answer, of course anything you run or do on your computer will incur a performance hit, however it will not be noticeable. I been using secure memory for years in Tiger and now Leopard and cannot see any performance hit. Not even worth benchmarking.
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Administrator Join Date: May 2000
Location: California
Status:
Offline
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I've got too much RAM installed to test this. 6.5 GB, with 3+ free after 31 days of uptime. We'd need someone with 512 MB to do a few trial runs.
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