On 03.12.24 13:06, Michal Hocko wrote:
On Mon 02-12-24 14:50:49, Frank van der Linden wrote:
On Mon, Dec 2, 2024 at 1:58 PM Mateusz Guzik <mjguzik@xxxxxxxxx> wrote:
Any games with "background zeroing" are notoriously crappy and I would
argue one should exhaust other avenues before going there -- at the end
of the day the cost of zeroing will have to get paid.
I understand that the concept of background prezeroing has been, and
will be, met with some resistance. But, do you have any specific
concerns with the patch I posted? It's pretty well isolated from the
rest of the code, and optional.
The biggest concern I have is that the overhead is payed by everybody on
the system - it is considered to be a system overhead regardless only
part of the workload benefits from hugetlb pages. In other words the
workload using those pages is not accounted for the use completely.
If the startup latency is a real problem is there a way to workaround
that in the userspace by preallocating hugetlb pages ahead of time
before those VMs are launched and hand over already pre-allocated pages?
In QEMU we support parallel preallocation, and even NUMA-aware
preallocation, to reduce VM startup times with hugetlb.
We discussed improvements as referred to by Mateusz to further speed up
preallocation, but for now parallel+NUMA-aware preallocation seems to do
the trick.
--
Cheers,
David / dhildenb
