Re: linux-next regression: SNP Guest boot hangs with certain cpu/mem config combination

[Ard Biesheuvel]

On Fri, 28 Mar 2025 at 11:54, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>
> On Fri, Mar 28, 2025 at 10:33:31AM +0100, Ard Biesheuvel wrote:
> > Can you quantify the speedup?
>
> Test is below. I run it 10 times on a VM without unaccepted memory. With
> and without has_unaccepted_memory() check in cond_accept_memory().
>
> The difference is not huge, but it is there:
>
> Without static branch:  Mean: 35559993 us, StdDev: 167264
> With static branch:     Mean: 35286227 us, StdDev: 207595
> Diff:                   -273766 us / -0.77%
>

Fair enough - I think this is pretty close to negligible, but I know
that other people may feel differently. At least we have documented
the justification for using a static key here.