1. cmaier's Avatar
    We're simply trying to determine if iphone implements vm. We've found hints of it, but at this point we're trying to create a working set larger than physical memory to see what happens.
    08-23-2007 03:08 PM
  2. zbop#IM's Avatar
    We're simply trying to determine if iphone implements vm. We've found hints of it, but at this point we're trying to create a working set larger than physical memory to see what happens.
    Well, I don't know anything about OSX or the iphone version of OSX, but based on the previous posts it seems like it implements demand-paging, not sure about page swapping.

    Testing this indirectly such as browsing or loading a video probably isn't going to tell you anything.

    Note, that if you implement any code to test this, you should at least write-fault all the pages in that region rather than just allocate. On most VM systems, allocation only results in a reservation against swap or reservation against memory depending on the OS and configuration. And if you just read-fault the pages, it may allocate-on-demand but free them as needed, which isn't a valid test.

    Good luck
    08-23-2007 03:22 PM
  3. cmaier's Avatar
    Somewhere back in the thread I mentioned we should write to the allocated memory (seems so long ago :-)

    My "javascript" test just allocates, because when I tried to force write-faults it quit the program - it thought it was stuck in an infinite loop (same happens on the desktop). Limitation in the javascript engine, i guess.

    I'm also assuming demand paging, but we haven't seen clear evidence of it yet (since we seem unable to use enough memory to get it do anything), and it does seem to pre-load its default working set, which speaks against a pure demand-paging implementation.
    08-23-2007 03:29 PM
  4. Mike Overbo's Avatar
    Well, I don't know anything about OSX or the iphone version of OSX, but based on the previous posts it seems like it implements demand-paging, not sure about page swapping.
    Oooh, could this be implemented as a function of notifyd, one of the daemon processes? from man 3 notify:

    A client using notify_check() to determine when to invalidate a cache.
    There's also the section on Shared Memory in apple's VM documentation. I believe that notifyd is the process that's used for governing shared memory...
    08-23-2007 03:55 PM
  5. cmaier's Avatar
    Cache is different than VM. I don't know what apple means by "shared memory" though it sounds like it would be the equivalent of shared code pages (something like windows dlls?)

    Unfortunately both cache and VM use some of the same terminology (at least in academic circles, which is where my knowledge of memory hierarchies is rooted), so it gets confusing.
    08-23-2007 04:20 PM
  6. oalvarez's Avatar
    think about how much we have learned in this thread's existance. we started with the 10 things that absolutely sucked about the iPhone and are ending with 10 things that many of us know nothing about.

    god love TreoCentral
    08-23-2007 08:51 PM
  7. mikec#IM's Avatar
    Over?

    Who said it was over?

    Was it over when the Germans bombed Pearl Harbor?

    No!

    It's not over until we say it's over!
    08-24-2007 02:18 AM
  8. AnteL0pe's Avatar
    Just curious what are you guys trying to prove?
    That pretty much sums up the entire thread.
    08-24-2007 02:25 AM
  9. surur's Avatar
    Just curious what are you guys trying to prove?
    That pretty much sums up the entire thread.
    In this particular instance its whether the iPhone is memory constrained or not, which would limit the size for example of the web pages it could load.

    In general, its about how the iPhone is not as great as it pretends to be.

    Surur
    08-24-2007 02:34 AM
  10. cmaier's Avatar
    The iPhone doesn't "pretend to be" anything. It's a phone. A mere tool. It doesn't hate you. It didn't beat you up in third grade. Now, Archie and Jobs might pretend it's greater than it is, but that's a different story entirely.

    As for me, I'm just happy I can write code for the thing to make it do what *I* want. The rest of the fools that bought them hoping that Apple will someday make it do what *they* want are... fools. Those who bought it because it already did what *they* want are not fools (but probably are a tad wealthy).

    To follow up on mikec's comment: I give this thread a zero point zero.
    08-24-2007 09:33 AM
  11. surur's Avatar
    The iPhone doesn't "pretend to be" anything.
    Steve Jobs said to expect three things: "an incredibly great cell phone," "the best iPod we've ever made" and "the Internet in your pocket."
    Surur
    08-24-2007 09:50 AM
  12. cmaier's Avatar
    Yes. You know the iPhone isn't Steve Jobs, right? I mean, I've seen them both in the same place at the same time.
    08-24-2007 09:53 AM
  13. oalvarez's Avatar
    Quote:
    Steve Jobs said to expect three things: "an incredibly great cell phone," "the best iPod we've ever made" and "the Internet in your pocket."

    Surur
    i'm not sure it's an incredibly great phone (definitely a good one), it might be the best iPod they've ever made, and it does offer an incredibly great internet experience while being very pocketable.

    so what was the point you were trying to make?
    08-24-2007 10:08 AM
  14. whmurray's Avatar
    Over?

    Who said it was over?

    Was it over when the Germans bombed Pearl Harbor?

    No!

    It's not over until we say it's over!
    Germans? Pearl Harbor?
    08-24-2007 10:17 AM
  15. surur's Avatar
    142 pages says all 3 claims can be disputed.

    Surur
    08-24-2007 10:19 AM
  16. cmaier's Avatar
    Germans? Pearl Harbor?
    Not familiar with the classics, I see.
    08-24-2007 10:26 AM
  17. cmaier's Avatar
    142 pages says all 3 claims can be disputed.

    Surur
    No. 143 pages says "iphone sucks!" "no it doesn't!" "yes it does!" "well, you're stupid!" "no i'm not!" "iphone sucks!" "wait, what side am I on?"
    08-24-2007 10:28 AM
  18. whmurray's Avatar
    In this particular instance its whether the iPhone is memory constrained or not, which would limit the size for example of the web pages it could load.

    In general, its about how the iPhone is not as great as it pretends to be.

    Surur
    Parkinson's law of storage says that data expands to fill the storage available. Most of the storage in my iPhone is filled with music, audiobooks, movies, and poccasts. iTunes just took everything that was on my 40G iPod and put it my iPhone. I spend zero time managing memory on my iPhone (OK, I chopped one movie that I have watched several times.)

    Most of the memory in my Treo is filled with applications and databases. I spend lots of time managing the available 3 gigs. I frequently try to install apps for which I do not have adequate storage. For example, I love Avantgo, find it near essential for using the web on the Treo. If I install it, no room for anythng else.

    Because of the better browser and UI on the iPhone, I do not need an application like Avantgo.

    While I never have enough, I feel less storage constrained on the iPhone than on the Treo. (I remember when a gig filled a box car and one could not move that boxcar a mile for the price of an iPhone. It took a year and half to read that gig if one could maintain rated speeds.)
    08-24-2007 10:48 AM
  19. whmurray's Avatar
    Not familiar with the classics, I see.
    lol
    08-24-2007 10:49 AM
  20. whmurray's Avatar
    142 pages says all 3 claims can be disputed.

    Surur
    Most assertions can be argued. That is what distinguishes them from facts.
    08-24-2007 10:52 AM
  21. surur's Avatar
    Parkinson's law of storage says that data expands to fill the storage available. Most of the storage in my iPhone is filled with music, audiobooks, movies, and poccasts. iTunes just took everything that was on my 40G iPod and put it my iPhone. I spend zero time managing memory on my iPhone (OK, I chopped one movie that I have watched several times.)

    Most of the memory in my Treo is filled with applications and databases. I spend lots of time managing the available 3 gigs. I frequently try to install apps for which I do not have adequate storage. For example, I love Avantgo, find it near essential for using the web on the Treo. If I install it, no room for anythng else.

    Because of the better browser and UI on the iPhone, I do not need an application like Avantgo.

    While I never have enough, I feel less storage constrained on the iPhone than on the Treo. (I remember when a gig filled a box car and one could not move that boxcar a mile for the price of an iPhone. It took a year and half to read that gig if one could maintain rated speeds.)
    We are not talking about storage (I hate storage being called memory ).We are talking about RAM.

    To save you reading 142 pages of speculation, I have contended that the iPhone, with 128 MB SDRAM, is RAM constrained, and therefore had a hard limit to the size and number of images it could load for example, and the number of large web pages it could have open simultaneously.

    Others have disputed this, saying the iPhone runs "real OSX", and therefore had virtual memory, which meant the apps could address much more memory than the device actually possessed.

    I said embedded devices hardly ever use virtual memory.

    Others said Apple thinks differently.

    In short, it turns out I was right.

    Surur
    08-24-2007 11:24 AM
  22. whmurray's Avatar
    ...........I still think web only apps will fail (if the only option on iPhone. Sun tried this route on desktop 15 years ago and got creamed. (That company is a true embarassment.
    Sun was ahead of their time. I think that you generalize and mix the success of the iPhone with that of web apps.

    Let me give you a data point. Intuit sells consumer tax software and a consumer tax web app. Users of the former are declining and users of the latter are growing. It is, in part, generational. My generation will install an application that we will only use once in order not to show our tax data to Intuit. Young people simply will not do that. Of course, they really have only wages and salary, a little interest income and take the standard deduction. But twenty years from now they will still do it the way they are learning today.

    I am planning a trip into New York City for next week. I plan to take my iPhone rather than my Treo. Therefore, I am doing with web apps things that I would do with local apps on the Treo. One of the things that I like is the ability to store my planning results with a simple bookmark. Another is that I do not have to worry about the currency of the database. Yet another is that the applications are richer.

    Since I have this 680 that I never use, I was planning to give it to my great nephew for his eleventh birthdsy. (Yes, I spoil him; that's my job.) I am sure that if I offer him the choice, he will choose the iPhone. It really is a better product for him. He has been synching his iPod since he was seven (He is on his second one). He cannot tell you why the iPhone is better for him but he knows.
    08-24-2007 11:36 AM
  23. Mike Overbo's Avatar
    142 pages says all 3 claims can be disputed.
    By the 1% of folks that are having problems: the failure rate of iphones is less than 1%, much lower than industry standards, according to Business Week.

    In this particular instance its whether the iPhone is memory constrained or not, which would limit the size for example of the web pages it could load.
    Surur
    Web page sizes are artificially limited to 10MB each, 8 pages max, according to Apple's documentation.
    08-24-2007 12:52 PM
  24. mikec#IM's Avatar
    Whmurray,

    Your nephew might be better served with a copy of "Animal House".
    08-24-2007 01:16 PM
  25. mikec#IM's Avatar
    Well, the Engadget folks have a post that the iPhone is now unlockable. (software to be available shortly?).

    They seem very giddy about this.

    I'm curious if Apple will zap this in the next update, despite the claims it's zap-proof.

    They will probably will have some code in iTunes that says "if phone number = n/a, they delete all and send us an email reporting the offender." ;-)
    08-24-2007 01:21 PM
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