Question

I was reading this interesting article regarding the display of the memory parameters in the iPhone and I noticed that among the various data return in addition to “active” “physical” “free” etc. etc. there is also the “purgeable” (const int = purgeablePages vmStats. purgeable_count;), I was wondering since this is precisely “purgeable” how is possible purge it? There is a command in objective-c to do this?

Thanks at all

Answer 1

These are kernel memory management statistics. The purgeable memory pages can be freed and thus reused by the kernel at any time. Since this is a kernel-internal thing and the related memory likely doesn’t belong to your process (if you haven’t allocated it) you cannot influence it.

You can allocate purgeable memory through vm_allocate, but this isn’t really documented and you are very unlikely to ever need it. The best “documentation” available seems to be a WebKit class that uses purgeable memory.