On 10/7/24 01:43, 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(-)
Hi Paolo,
Thanks for fixing this.
Series:
Reviewed-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
I was wondering why we have a specific flags path for x64.
People who are interested in getting machine specific binaries can
always play with CFLAGS, so what was the original intent here?
Thanks,
Pierrick
