Virtual memory utility?

Discussion in 'iPad Hacking' started by gedansky, Jul 28, 2012.

  1. gedansky
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    gedansky iPF Novice

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    "Back in the day", when memory was expensive and hard to upgrade, there was a common practice of using something called "virtual memory" where a certain amount of hard disk space was allotted to compensate for lower than preferable levels of RAM. It wasn't ideal, but it did help.

    Then when Windows Mobile PDA devices really took off (think HP iPac), you could go into stock system settings and decide what percentage of overall memory (say, 64mb total) would be assigned as RAM, and what percentage would be assigned as storage, with 50/50 being the bottom limit. What this said was, when your memory is RAM and your storage is RAM, it's just a matter of semantics, how you choose to divvy it up.

    So... why not the iPad? For instance, There is 256mb of RAM allotted as RAM on the original iPad, and, in my case, 64GB of RAM allotted as storage. It should be possible, and perfectly easy, to create a utility that does exactly what the earlier Windows Mobile PDA's could do... Let you decide how you want to allot your memory and storage. Maybe it could work on a stock device. Maybe (probably) it would need to be jailbroken. It doesn't really matter to me.

    Unfortunately, all I have found on Virtual Memory for the iPad, is a process, through jailbreaking, that uses remaining ROM (up to 80mb) for swap files. But, this is not a lot of space to be worth the trouble, and tends to crash devices. As I remember from my Palm days, borrowing unused ROM space was NOT the best solution. It's much better to decide that you want to give up a gb or two of your main storage to be reallocated as RAM, as I did with my HP iPac running WinMo 2003. This would be amazing and I know it's not that complex, and has been part of Windows mobile devices for over 10 years.
  2. f4780y
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    f4780y Super Moderator Staff Member

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    Yes, there have been virtual memory tweaks for the iPad1 when it was originally jailbroken, However, it simply is not as effective as you think it might be for a variety of reasons.
    IOS had the facility built in by creating a com.apple.dynamic_pager.plist file in /System/Library/LaunchDaemons, where you could allocate as much storage as you liked to a swap partition. There were also a couple of dedicated JB tweaks for 3.x, and maybe 4.x, but I believe these are all long gone now.

    The results betrayed the reason it was not pursued. SSD is "slow" (in terms of write) and virtual memory requires a lot of writing. The OS and Apps would demonstrate some lag as memory was swapped. This would be anywhere from less than a second, up to 30+ seconds which would compromise the user experience considerably. Battery also took a small hit (more important on the iPhone of course).
    Overall, it just didn't provide the benefit that folks thought it would. Certainly not something that could be classified as "amazing". Lag is not a good tradeoff to keeping more apps in memory, and by the time you got past the lag, in many cases, a stock device would have re-loaded the app in to memory in any case...

    Furthermore, the memory management in IOS has improved considerably over the generations and it is generally just better at managing apps and memory now. With 256MB RAM, iPad12 owners suffer the most of course.

    Backgrounder is probably the best jailbreak solution if you are intent on keeping as many things as possible in RAM and running. You should certainly look into that, but you really need a "use case" for it. Just keeping everything running for the sake of it or because you 'can', as folks found out, isn't all it is cracked up to be :)

    Also, I'm not sure how virtual memory can ever use ROM? The secret is in the name. It's read-only ;)
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  3. twerppoet
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    twerppoet iPad Legend

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    Thanks. I'm feeling almost edumucated. :)
  4. gedansky
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    gedansky iPF Novice

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    Thanks so much for the detailed explanation. Honestly, I'm not interested in keeping too many things open and running, I actually close apps whenever I can. I just want to improve speed and reduce lag, which usually requires a combination of closing apps and rebooting. I am running iOS 4.3.5, which, though slightly lackluster by comparison, is much faster and smoother running, and much less of a battery hog, than 5.1.1. I know this because I ran 5.11 until recently when I needed an Apple Care replacement, and my "new" iPad 1, was preloaded with 4.3.5, which I am reluctant to change unless there are tweaks that seriously compensate for the lag and the poor battery life inherent at that level, particularly on the iPad 1.

    As for the question about virtual memory using ROM, I can explain...when ROM is written to, it is flashed at a higher than usual temperature which literally burns on a data image. With early Palm devices, before SD cards, backup software would burn a copy of your PIM and other key data, along with a recovery icon onto ROM. So, if your Palm device lost data, you could trigger a restore from ROM. This backup, by the way, could be made several times daily. I'm sure it shortened the life of the device, but it kept you from being stranded, as I was once, in NYC with an empty Palm Phone and my local contact's numbers gone. Long story longer, apparently the virtual memory solutions I stumbled upon takes similar advantage of 80mb of free ROM in the IPad 1. To me, 80mb is hardly worth consideration. But, if I could move a slider and assign 2gb of data to dramatically speed up my iPad, that would be worth it,

    Thanks again!
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