Message ID | 20241007084342.1264048-1-pbonzini@redhat.com |
---|---|
Headers | show |
Series | meson: ensure we enable CMPXCHG128 on x86_64 | expand |
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.bouvier@linaro.org> > Supersedes: <20241004220123.978938-1-pierrick.bouvier@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 <mjt@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
Paolo Bonzini <pbonzini@redhat.com> writes: > 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.bouvier@linaro.org> > Supersedes: <20241004220123.978938-1-pierrick.bouvier@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Tested-by: Alex Bennée <alex.bennee@linaro.org>