Re: Request for clarification regarding huge pages and remapping of virtual to physical address

[sunil bhargo <marx_bhargav@yahoo.com>]

[-- Attachment #1: Type: text/plain, Size: 1331 bytes --]

 David,Thanks for your response. So if i get it right then reserving the memory at boot time with/without the huge page, the page migration can happen ? 

Thanks,Sunil Bhargo

    On Wednesday, April 17, 2024 at 02:47:30 PM GMT+5:30, David Hildenbrand <david@redhat.com> wrote:  
 
 On 17.04.24 11:11, sunil bhargo wrote:
> Hi,
> 
> We have an application which relies on virtual address to physical 
> address mapping to remain static. The buffer is allocated using 
> malloc. It is in user space and we were using the mlock thinking that as 
> it would prevent the swapping the va->pa address mapping would be 
> static. But it seems to be a faulty assumption.
> 
> If the memory is allocated from huge pages by reserving space upfront at 
> the kernel boot up and then mmap’ing using MAP_HUGETLB, is it assured 
> that virtual address to physical mapping won’t be remapped and will be 
> static ?

Unless you have a kernel that has page migration disabled, no.

You could use secretmem (which is currently not migratabale/swappable/ 
...), but that has very limited capabilities.

A "hack" would be to register that (ordinary) memory using iouring as a 
fixed buffer. That way, it will be longterm pinned and can neither get 
migrated nor swapped out.

-- 
Cheers,

David / dhildenb

  

[-- Attachment #2: Type: text/html, Size: 2789 bytes --]