Because that's what configure used to do ( https://lists.nongnu.org/archive/html/qemu-devel/2022-02/msg00650.html)...
It can surely be changed but AVX512 is known to limit processor frequency. I am not sure if the limitation is per core or extends to multiple cores, and it would be a pity if guests were slowed down even further during migration. Especially after the bulk phase buffer_is_zero performance matters a lot less so you'd pay the price of AVX512 for little gain. After the bulk phase it may even make sense to just use SSE, since even AVX requires a voltage transition[1] from what I saw at https://travisdowns.github.io/blog/2020/01/17/avxfreq1.html. Paolo [1] voltage transitions slow down the processor during the transition Il dom 4 dic 2022, 02:51 Richard Henderson <richard.hender...@linaro.org> ha scritto: > I'm not sure why this option wasn't set the same as avx2. > > Signed-off-by: Richard Henderson <richard.hender...@linaro.org> > --- > meson_options.txt | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/meson_options.txt b/meson_options.txt > index 4b749ca549..f98ee101e2 100644 > --- a/meson_options.txt > +++ b/meson_options.txt > @@ -102,7 +102,7 @@ option('membarrier', type: 'feature', value: > 'disabled', > > option('avx2', type: 'feature', value: 'auto', > description: 'AVX2 optimizations') > -option('avx512f', type: 'feature', value: 'disabled', > +option('avx512f', type: 'feature', value: 'auto', > description: 'AVX512F optimizations') > option('keyring', type: 'feature', value: 'auto', > description: 'Linux keyring support') > -- > 2.34.1 > >
