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@xxxxxxxxxx> 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
> 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
