Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 31 Jan 2018 13:00:35 -0800 | Subject | Re: [PATCH] x86: Align TLB invalidation info |
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On Wed, Jan 31, 2018 at 12:48 PM, Nadav Amit <nadav.amit@gmail.com> wrote: > Andy Lutomirski <luto@amacapital.net> wrote: > >> >> >>> On Jan 31, 2018, at 12:11 PM, Nadav Amit <namit@vmware.com> wrote: >>> >>> The TLB invalidation info is allocated on the stack, which might cause >>> it to be unaligned. Since this information may be transferred to >>> different cores for TLB shootdown, this might result in an additional >>> cache-line bouncing between the cores. >>> >>> GCC provides a way to deal with it by using >>> __builtin_alloca_with_align(). Use it to avoid the bouncing cache lines. >> >> Eww. How about __aligned? > > Err.. Stupid me. For some reason I remembered I tried it and it didn’t have > the desired effect, which caused me to assume it does not work for variables > on the stack. Anyhow, it does the work. I’ll submit v2. >
You're probably remembering that __aligned(16) malfunctions on older GCC versions. But __aligned(64), which is what you want, has always been okay AFAIK.
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