Re: [PATCH kvm-unit-tests] scripts: Speedup MAX_SMP check

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On Mon, Sep 03, 2018 at 12:58:45PM +0200, Christoffer Dall wrote:
> The current MAX_SMP check launches QEMU for every value of the SMP
> parameter to check if the SMP parameter based on the native is higher
> than the QEMU maximum supported configuration.
> 
> On something like a TX2, which has 224 threads, this takes a very long
> time where the test script just sits there with no output.
> 
> Reduce the wait time by taking the log2 of MAX_SMP in each iteration of
> the loop instead.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
> ---
>  scripts/runtime.bash | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/runtime.bash b/scripts/runtime.bash
> index a31ae91..1e2c288 100644
> --- a/scripts/runtime.bash
> +++ b/scripts/runtime.bash
> @@ -140,5 +140,5 @@ function run()
>  # just remove it...
>  while $RUNTIME_arch_run _NO_FILE_4Uhere_ -smp $MAX_SMP \
>  		|& grep -qi 'exceeds max CPUs'; do
> -	((--MAX_SMP))
> +	MAX_SMP=$((MAX_SMP >> 1))
>  done
> -- 
> 2.7.4
>

Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>


Someday I should move this into arch-specific code and replace
it with something like:

if gic-v3
  MAX_SMP = MIN(_SC_NPROCESSORS_ONLN, 255)
else
  MAX_SMP = MIN(_SC_NPROCESSORS_ONLN, 8)

If other archs ever care about it (they currently don't), then
they can implement their own thing.

Thanks,
drew



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