Question

i have see this article about retrieve memory usage off iphone app
programmatically-retrieve-memory-usage-on-iphone It’s great !

In my project i want to retrieve the available VRAM free, because my app load many textures, and i must preload theses into the video Ram for fast rendering.

but on the VM_statistics i don’t view theses properties : vm_statistics MAN page

Thanks a lot for your help.

Answer 1

As you’ve seen so far, getting hard numbers for GL texture memory usage is quite difficult. It’s complicated further by the fact that CoreAnimation will also use GL Texture memory without “consulting” you, including from processes other than yours.

Practically speaking, I suggest that you use the VM Tracker instrument in Instruments to watch changes in the VM pages your process maps under the IOKit tag. It’s a bit crude, but it’s the best approach I’ve found. In my experience, this process is largely guess and check.

You asked specifically for a way to determine the amount of free VRAM, but even if you could get that info, it’s not really likely to be helpful. Even if your app is totally OpenGL and uses no UIViews or CoreAnimation layers other processes, most importantly those more privileged than yours, can consume that memory at any time, either explicitly or implicitly through CoreAnimation. It’s also probably safe to assume that if your app prevents those more-privileged apps from getting the texture memory they need, your process will be killed.

Put differently, even if you could ascertain the instantaneous state of the GL texture memory, you probably couldn’t count on being the only consumer of that resource, so it’s pretty useless.

At the end of the day, you should spend your effort designing your app to be a good citizen in terms of GL memory and manage (read: minimize) your own consumption of texture memory. iOS devices are not old-school game consoles — you are not the only thing running — so you need to be mindful and tolerant of that fact, lest your app be one of those where everyone has to reboot their phone every few minutes in order to use it.