Re: Change default VM address
Re: Change default VM address
- Subject: Re: Change default VM address
- From: Shantonu Sen <email@hidden>
- Date: Mon, 12 Sep 2011 23:26:48 -0700
A side effect is that you might not notice truncation of 64-bit pointers if all of your app's static text and data are below 4GB.
There's also a performance penalty to linking 64-bit programs in the low 4GB of the address space when run with the 32-bit kernel, since the kernel is forced to do TLB flushes on transitions into the kernel. The default behavior allows for the flush to be avoided.
Shantonu
On Sep 12, 2011, at 10:50 PM, comex wrote:
> 2011/9/12 José Cornado <email@hidden>:
>> First of all, I apologize if this is not the correct list and if this
>> somehow a novice question. If there is a better suited list, please let me
>> know.
>>
>> If I wanted to change the default initial value of the VM address
>> (executable) from 0x100000000 to another lower number, is this possible? Is
>> this a linker option or compiler option? If possible, which side-effects
>> could have?
>
> You can use this, but why do you want to do it?
>
> -image_base address
> Specifies the perferred load address for a dylib or
> bundle. The argument address is a hexadecimal number with
> an optional leading 0x. By choosing non-overlapping
> address for all dylibs and bundles that a program loads,
> launch time can be improved because dyld will not
> need to "rebase" the image (that is, adjust pointers within
> the image to work at the loaded address). It is
> often easier to not use this option, but instead use the
> rebase(1) tool, and give it a list of dylibs. It
> will then choose non-overlapping addresses for the list and
> rebase them all. This option is also called
> -seg1addr for compatibility.
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