Intel Working On 5-Level Paging To Increase Linux Virtual/Physical Address Space

[phoronix]

Phoronix: Intel Working On 5-Level Paging To Increase Linux Virtual/Physical Address Space

Intel developers are working on "five level paging" to overcome the x86_64 limitation of 256 TiB of virtual address space and 64 TiB of physical address space. While you may not have that much memory in your desktop, that limitation is being hit but can be increased through 5-level paging...

http://www.phoronix.com/scan.php?page=news_item&px=Intel-5-Level-Paging

[davidbepo]

i heard somewhere that this increases complexity and reduces performance
is it true?

[birdie]

I wonder why they can't just increase memory pages bitness of their CPUs. Known as 64bit, they only use/have 48 bits for pages.

The AMD64 architecture defines a 64-bit virtual address format, of which the low-order 48 bits are used in current implementations.^[1](p120) This allows up to 256 TB (2⁴⁸bytes) of virtual address space. The architecture definition allows this limit to be raised in future implementations to the full 64 bits,^{[1](p2)(p3)(p13)(p117)(p120)} extending the virtual address space to 16 EB (2⁶⁴ bytes). This is compared to just 4 GB (2³² bytes) for the x86.^[15]

[Serafean]

i heard somewhere that this increases complexity and reduces performance
is it true?

Every level of indirection does that. By how much remains to be measured.

[cRaZy-bisCuiT]

So the Intel guys are just bored? WTF will need this within the next 5 years?

[Chewi]

So the Intel guys are just bored? WTF will need this within the next 5 years?

Well the UK government need something to host all that data they're now collecting on its citizens.

[Azpegath]

Relevant XKCD strip:

https://xkcd.com/619/

[defaultUser]

So the Intel guys are just bored? WTF will need this within the next 5 years?

There are options using this much of RAM and actually being limited by this restriction, for instance (https://www.sgi.com/products/servers/uv/). Another possible use for these expanded limits is the introduction of technology like the 3D xpoint.

[starshipeleven]

Relevant XKCD strip:
https://xkcd.com/619/

for those that didn't know yet: Desktop isn't main linux target.

[Azpegath]

for those that didn't know yet: Desktop isn't main linux target.

For those that didn't know yet: You're boring.