Re: [Qemu-devel] [PATCH v6 73/73] cputlb: queue async flush jobs without the BQL

["Alex Bennée" <alex.bennee@linaro.org>]

Emilio G. Cota <cota@braap.org> writes:

> This yields sizable scalability improvements, as the below results show.
>
> Host: Two Intel E5-2683 v3 14-core CPUs at 2.00 GHz (Haswell)
>
> Workload: Ubuntu 18.04 ppc64 compiling the linux kernel with
> "make -j N", where N is the number of cores in the guest.

I can verify my pigz benchmark starts levelling out at 12-14 guest vCPUs
on the 36 core host box I'm testing on. Not super controlled environment
but certainly showing how far MTTCG has come since it was first
introduced. Good stuff.

> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index dad9b7796c..8491d36bcf 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -260,7 +260,7 @@ static void flush_all_helper(CPUState *src, run_on_cpu_func fn,
>
>      CPU_FOREACH(cpu) {
>          if (cpu != src) {
> -            async_run_on_cpu(cpu, fn, d);
> +            async_run_on_cpu_no_bql(cpu, fn, d);
>          }
>      }
>  }
> @@ -336,8 +336,8 @@ void tlb_flush_by_mmuidx(CPUState *cpu, uint16_t idxmap)
>      tlb_debug("mmu_idx: 0x%" PRIx16 "\n", idxmap);
>
>      if (cpu->created && !qemu_cpu_is_self(cpu)) {
> -        async_run_on_cpu(cpu, tlb_flush_by_mmuidx_async_work,
> -                         RUN_ON_CPU_HOST_INT(idxmap));
> +        async_run_on_cpu_no_bql(cpu, tlb_flush_by_mmuidx_async_work,
> +                                RUN_ON_CPU_HOST_INT(idxmap));
>      } else {
>          tlb_flush_by_mmuidx_async_work(cpu, RUN_ON_CPU_HOST_INT(idxmap));
>      }
> @@ -481,8 +481,8 @@ void tlb_flush_page_by_mmuidx(CPUState *cpu, target_ulong addr, uint16_t idxmap)
>      addr_and_mmu_idx |= idxmap;
>
>      if (!qemu_cpu_is_self(cpu)) {
> -        async_run_on_cpu(cpu, tlb_flush_page_by_mmuidx_async_work,
> -                         RUN_ON_CPU_TARGET_PTR(addr_and_mmu_idx));
> +        async_run_on_cpu_no_bql(cpu, tlb_flush_page_by_mmuidx_async_work,
> +                                RUN_ON_CPU_TARGET_PTR(addr_and_mmu_idx));
>      } else {
>          tlb_flush_page_by_mmuidx_async_work(
>              cpu, RUN_ON_CPU_TARGET_PTR(addr_and_mmu_idx));


Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>

I think that brings my run through this patch series to a conclusion.
Looking good all round.

--
Alex Bennée