svn commit: r221855 - in head/sys: amd64/include arm/include dev/md dev/null i386/include ia64/include mips/include powerpc/include sparc64/include sun4v/include sys vm

[Alan Cox]

On 5/13/2011 2:40 PM, Kostik Belousov wrote:
> On Fri, May 13, 2011 at 07:35:01PM +0000, Matthew D Fleming wrote:
>> Author: mdf
>> Date: Fri May 13 19:35:01 2011
>> New Revision: 221855
>> URL: http://svn.freebsd.org/changeset/base/221855
>>
>> Log:
>>    Move the ZERO_REGION_SIZE to a machine-dependent file, as on many
>>    architectures (i386, for example) the virtual memory space may be
>>    constrained enough that 2MB is a large chunk.  Use 64K for arches
>>    other than amd64 and ia64, with special handling for sparc64 due to
>>    differing hardware.
>>
>>    Also commit the comment changes to kmem_init_zero_region() that I
>>    missed due to not saving the file.  (Darn the unfamiliar development
>>    environment).
>>
>>    Arch maintainers, please feel free to adjust ZERO_REGION_SIZE as you
>>    see fit.
>>
>>    Requested by:	alc
>>    MFC after:	1 week
>>    MFC with:	r221853
> Wasting 2MB even on amd64 is not quite good, IMHO.

It's virtual address space, of which we have 512GB on amd64, and not 
physical memory.  Only one page of physical memory is used.

Alan