Wow. Thanks!
> On Dec 9, 2015, at 18:28 , Britt Durbrow
> <bdurb...@rattlesnakehillsoftworks.com> wrote:
>
> Well, FWIW I happen to have an iPad Pro sitting next to me, so I just whipped
> up the following test and was able to allocate and write to almost 3GB of RAM
> before it started crashing on me.
>
> #define allocationSize (1024ULL*1024ULL*3050ULL)
> #define stride (4096)
>
> - (BOOL)application:(UIApplication *)application
> didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
> {
>
> printf("Starting memory test...\n");
>
> printf("Allocating memory...\n");
>
> uint8_t *buffer=malloc(allocationSize);
>
> printf("Writing to buffer...\n");
>
> for(uint64_t cursor=0; cursor<allocationSize; cursor+=stride)
> buffer[cursor]=0xAC;
>
> printf("Done!\n");
>
>
> return YES;
> }
>
>
>
>> On Dec 9, 2015, at 5:56 PM, Rick Mann <rm...@latencyzero.com> wrote:
>>
>>
>>> On Dec 9, 2015, at 17:37 , Jens Alfke <j...@mooseyard.com> wrote:
>>>
>>>
>>>> On Dec 9, 2015, at 5:17 PM, Rick Mann <rm...@latencyzero.com> wrote:
>>>>
>>>> - By "virtual memory," I'm sure you don't mean it's swapping to disk
>>>> (flash). Or do you? If not, how is it virtual?
>>>
>>> All memory is virtual in any modern OS — the only thing that sees ‘real’
>>> memory addresses is the kernel’s VM subsystem. ‘Virtual’ just means there’s
>>> a layer of indirection between address space and RAM.
>>>
>>> On iOS it’s just that the address space normally allocated to apps (by
>>> malloc, etc.) isn’t backed by a swap file. So it doesn’t get paged out, but
>>> it’s also limited by the amount of physical RAM.
>>
>> Ah, yes, of course. Just the address translation is happening. Yeah, I need
>> to know if the dirty limit has increased.
>>
>> Alternatively, if mmap-ed memory would actually live in RAM, but get around
>> the dirty limit (assuming for the sake of argument that the user isn't
>> running other apps), then we really could get more memory without a speed
>> penalty via mmap().
>>
>>>
>>> By “how much virtual memory you can use” I believe Rick means how much
>>> _address space_.
>>
>> No, I need to know how much I can actually allocate and dirty.
>>
>>
>> --
>> Rick Mann
>> rm...@latencyzero.com
>>
>>
>>
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>
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--
Rick Mann
rm...@latencyzero.com
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