Re: [PATCH v2 8/9] x86/mm/tlb: Remove UV special case

Thomas Gleixner
2019-07-09T19:50:42Z

On Tue, 2 Jul 2019, Nadav Amit wrote:

> SGI UV support is outdated and not maintained, and it is not clear how
> it performs relatively to non-UV. Remove the code to simplify the code.

You should at least Cc the SGI/HP folks on that. They are still
around. Done so.

> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Suggested-by: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Nadav Amit <namit@vmware.com>
> ---
> arch/x86/mm/tlb.c | 25 -------------------------
> 1 file changed, 25 deletions(-)
>
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index b47a71820f35..64afe1215495 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -689,31 +689,6 @@ void native_flush_tlb_multi(const struct cpumask *cpumask,
> trace_tlb_flush(TLB_REMOTE_SEND_IPI,
> (info->end - info->start) >> PAGE_SHIFT);
>
> - if (is_uv_system()) {
> - /*
> - * This whole special case is confused. UV has a "Broadcast
> - * Assist Unit", which seems to be a fancy way to send IPIs.
> - * Back when x86 used an explicit TLB flush IPI, UV was
> - * optimized to use its own mechanism. These days, x86 uses
> - * smp_call_function_many(), but UV still uses a manual IPI,
> - * and that IPI's action is out of date -- it does a manual
> - * flush instead of calling flush_tlb_func_remote(). This
> - * means that the percpu tlb_gen variables won't be updated
> - * and we'll do pointless flushes on future context switches.
> - *
> - * Rather than hooking native_flush_tlb_multi() here, I think
> - * that UV should be updated so that smp_call_function_many(),
> - * etc, are optimal on UV.
> - */
> - flush_tlb_func_local(info);
> -
> - cpumask = uv_flush_tlb_others(cpumask, info);
> - if (cpumask)
> - smp_call_function_many(cpumask, flush_tlb_func_remote,
> - (void *)info, 1);
> - return;
> - }
> -
> /*
> * If no page tables were freed, we can skip sending IPIs to
> * CPUs in lazy TLB mode. They will flush the CPU themselves
> --
> 2.17.1
>
>