Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings()

[Steven Rostedt]

On Tue, 12 May 2020 17:02:50 +0200
Joerg Roedel <jroedel@xxxxxxx> wrote:

> On Mon, May 11, 2020 at 12:36:19PM -0700, Andy Lutomirski wrote:
> > Iâm guessing the right solution is either your series or your series
> > plus preallocation on 64-bit. Iâm just grumpy about it...  
> 
> Okay, so we can do the pre-allocation when it turns out the pgd_list
> lock-times become a problem on x86-64. The tracking code in vmalloc.c is
> needed anyway for 32-bit and there is no reason why 64-bit shouldn't use
> it as well for now.
> I don't think that taking the lock _will_ be a problem, as it is only
> taken when a new PGD/P4D entry is populated. And it is pretty unlikely
> that a system will populate all 64 of them, with 4-level paging each of
> these entries will map 512GB of address space. But if I am wrong here
> pre-allocating is still an option.
> 

256TB of RAM isn't too far in the future ;-)

-- Steve