Re: [PATCH] x86: Align TLB invalidation info

[Dave Hansen]

On 01/31/2018 12:48 PM, Nadav Amit wrote:
>>> On Jan 31, 2018, at 12:11 PM, Nadav Amit <namit@xxxxxxxxxx> 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 didnât have
> the desired effect, which caused me to assume it does not work for variables
> on the stack. Anyhow, it does the work. Iâll submit v2.

Also, just curious, but did you find this situation by inspection or did
it show up in a profile somewhere?