07.10.2024 11:43, Paolo Bonzini wrote:
Alex discovered that CMPXCHG128 was not enabled when building for x86_64, resulting in slow execution for wide atomic instructions, creating a huge contention when combined with a high number of cpus (found while booting android aarch64 guest on x86_64 host). The problem is that even though we enable -mcx16 option for x86_64, this is not used when testing for CMPXCHG128. Thus, we silently turn it off. x86_64 is the only architecture adding machine flags for now, so the problem is limited to this host architecture. However, the problem is generic, so define a new variable for all the -m options, so that they can be used for other such tests in the future. Based-on: <20241004223715.1275428-1-pierrick.bouv...@linaro.org> Supersedes: <20241004220123.978938-1-pierrick.bouv...@linaro.org> Paolo Bonzini (2): meson: define qemu_isa_flags meson: ensure -mcx16 is passed when detecting ATOMIC128 meson.build | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-)
Series: Reviewed-By: Michael Tokarev <m...@tls.msk.ru> Yeah, this is exactly what I thought about when replying to email by Pierrick Bouvier. Well, with less details ofc :) Thanks, /mjt
