Phil Carmody on Sat, 27 Jan 2007 02:21:33 +0100

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Re: GMP build on OSX

--- Vincent Lefevre <> wrote:
> On 2007-01-26 17:03:16 +0100, Bill Allombert wrote:
> > Probably neither (directly). Blanking pages is the duty of the
> > kernel and occurs when memory is requested. It is probably caused by
> > the malloc library (normally part of the C library) . Maybe you
> > could try alternative malloc libraries or alternative OS.
> Page-zeroing should be done by the kernel for obvious security reasons.
> This means that whatever C library is used, pages will be zeroed. So,
> changing the malloc library probably won't have any effect, unless the
> default library does reads/writes or something else to make sure that
> the memory is really allocated (and not just address space like under
> Linux). But I don't know what the policy is under Mac OS X and I've
> never done any test about that.

However, so far the kernel has zeroed 10^13 bytes of memory for my single
process. Given that the process only has a memory footprint of ~150MB, that's
9,999,850MB of unnecessary zeroing of memory, causing a 20% performance hit.

When my processor goes idle, I'll try the non-GMP kernel, and see if it makes
any difference. I'll also see if alloca makes a difference in GMP.


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