Messages in this thread | | | Subject | Re: [PATCH] x86: Align TLB invalidation info | From | Dave Hansen <> | Date | Wed, 31 Jan 2018 13:01:24 -0800 |
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On 01/31/2018 12:11 PM, Nadav Amit 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.
It doesn't really *bounce*, though, does it? I don't see any writes on the remote side. The remote use seems entirely read-only.
You also don't have to exhaustively test this, but I'd love to see at least a sanity check with a microbenchmark (or something) that, yes, this does help *something*. Maybe it makes the remote flush_tlb_func_common() run faster because it's pulling in fewer lines, or maybe you can even detect fewer misses in there.
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