[PATCH 02/10] ARM: tlb: don't perform inner-shareable invalidation for local TLB ops
Jonathan Austin
jonathan.austin at arm.com
Thu Jun 13 13:50:03 EDT 2013
Hi Will,
On 06/06/13 15:28, Will Deacon wrote:
> Inner-shareable TLB invalidation is typically more expensive than local
> (non-shareable) invalidation, so performing the broadcasting for
> local_flush_tlb_* operations is a waste of cycles and needlessly
> clobbers entries in the TLBs of other CPUs.
>
> This patch introduces __flush_tlb_* versions for many of the TLB
> invalidation functions, which only respect inner-shareable variants of
> the invalidation instructions. This allows us to modify the v7 SMP TLB
> flags to include *both* inner-shareable and non-shareable operations and
> then check the relevant flags depending on whether the operation is
> local or not.
I think this approach leaves us in trouble for some SMP_ON_UP cores as
the IS versions of the instructions don't exist for them.
Is there something that should be ensuring your new __flush_tlb*
functions don't get called for SMP_ON_UP? If not it looks like we might
need to do some runtime patching with the ALT_SMP/ALT_UP macros...
I've commented on one of the example inline below...
>
> This gains us around 0.5% in hackbench scores for a dual-core A15, but I
> would expect this to improve as more cores (and clusters) are added to
> the equation.
>
> Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
> Reported-by: Albin Tonnerre <Albin.Tonnerre at arm.com>
> Signed-off-by: Will Deacon <will.deacon at arm.com>
> ---
> arch/arm/include/asm/tlbflush.h | 67 ++++++++++++++++++++++++++++++++++++++---
> arch/arm/kernel/smp_tlb.c | 8 ++---
> arch/arm/mm/context.c | 6 +---
> 3 files changed, 68 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm/include/asm/tlbflush.h b/arch/arm/include/asm/tlbflush.h
> index a3625d1..55b5e18 100644
> --- a/arch/arm/include/asm/tlbflush.h
> +++ b/arch/arm/include/asm/tlbflush.h
> @@ -167,6 +167,8 @@
> #endif
>
> #define v7wbi_tlb_flags_smp (TLB_WB | TLB_BARRIER | \
> + TLB_V6_U_FULL | TLB_V6_U_PAGE | \
> + TLB_V6_U_ASID | \
> TLB_V7_UIS_FULL | TLB_V7_UIS_PAGE | \
> TLB_V7_UIS_ASID | TLB_V7_UIS_BP)
> #define v7wbi_tlb_flags_up (TLB_WB | TLB_DCLEAN | TLB_BARRIER | \
> @@ -330,6 +332,21 @@ static inline void local_flush_tlb_all(void)
> tlb_op(TLB_V4_U_FULL | TLB_V6_U_FULL, "c8, c7, 0", zero);
> tlb_op(TLB_V4_D_FULL | TLB_V6_D_FULL, "c8, c6, 0", zero);
> tlb_op(TLB_V4_I_FULL | TLB_V6_I_FULL, "c8, c5, 0", zero);
> +
> + if (tlb_flag(TLB_BARRIER)) {
> + dsb();
> + isb();
> + }
> +}
> +
> +static inline void __flush_tlb_all(void)
> +{
> + const int zero = 0;
> + const unsigned int __tlb_flag = __cpu_tlb_flags;
> +
> + if (tlb_flag(TLB_WB))
> + dsb();
> +
> tlb_op(TLB_V7_UIS_FULL, "c8, c3, 0", zero);
I think we can get away with something similar to what we do in the
cache maintenance case here, using ALT_SMP and ALT_UP to do runtime code
patching and use TLB_V6_U_* for the UP case...
A follow on question is whether we still need to keep the *non* unified
TLB maintenance operations (eg DTLBIALL, ITLBIALL). As far as I can see
looking in to old TRMs, the last ARM CPU that didn't automatically treat
those I/D ops to unified ones was ARM10, so not relevant here...
But - do some of the non-ARM cores exploit the (now deprecated) option
to maintain these separately? Also did I miss some more obscure ARM variant?
Jonny
>
> if (tlb_flag(TLB_BARRIER)) {
> @@ -348,21 +365,32 @@ static inline void local_flush_tlb_mm(struct mm_struct *mm)
> dsb();
>
> if (possible_tlb_flags & (TLB_V4_U_FULL|TLB_V4_D_FULL|TLB_V4_I_FULL)) {
> - if (cpumask_test_cpu(get_cpu(), mm_cpumask(mm))) {
> + if (cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
> tlb_op(TLB_V4_U_FULL, "c8, c7, 0", zero);
> tlb_op(TLB_V4_D_FULL, "c8, c6, 0", zero);
> tlb_op(TLB_V4_I_FULL, "c8, c5, 0", zero);
> }
> - put_cpu();
> }
>
> tlb_op(TLB_V6_U_ASID, "c8, c7, 2", asid);
> tlb_op(TLB_V6_D_ASID, "c8, c6, 2", asid);
> tlb_op(TLB_V6_I_ASID, "c8, c5, 2", asid);
> +
> + if (tlb_flag(TLB_BARRIER))
> + dsb();
> +}
> +
> +static inline void __flush_tlb_mm(struct mm_struct *mm)
> +{
> + const unsigned int __tlb_flag = __cpu_tlb_flags;
> +
> + if (tlb_flag(TLB_WB))
> + dsb();
> +
> #ifdef CONFIG_ARM_ERRATA_720789
> - tlb_op(TLB_V7_UIS_ASID, "c8, c3, 0", zero);
> + tlb_op(TLB_V7_UIS_ASID, "c8, c3, 0", 0);
> #else
> - tlb_op(TLB_V7_UIS_ASID, "c8, c3, 2", asid);
> + tlb_op(TLB_V7_UIS_ASID, "c8, c3, 2", ASID(mm));
> #endif
>
> if (tlb_flag(TLB_BARRIER))
> @@ -392,6 +420,21 @@ local_flush_tlb_page(struct vm_area_struct *vma, unsigned long uaddr)
> tlb_op(TLB_V6_U_PAGE, "c8, c7, 1", uaddr);
> tlb_op(TLB_V6_D_PAGE, "c8, c6, 1", uaddr);
> tlb_op(TLB_V6_I_PAGE, "c8, c5, 1", uaddr);
> +
> + if (tlb_flag(TLB_BARRIER))
> + dsb();
> +}
> +
> +static inline void
> +__flush_tlb_page(struct vm_area_struct *vma, unsigned long uaddr)
> +{
> + const unsigned int __tlb_flag = __cpu_tlb_flags;
> +
> + uaddr = (uaddr & PAGE_MASK) | ASID(vma->vm_mm);
> +
> + if (tlb_flag(TLB_WB))
> + dsb();
> +
> #ifdef CONFIG_ARM_ERRATA_720789
> tlb_op(TLB_V7_UIS_PAGE, "c8, c3, 3", uaddr & PAGE_MASK);
> #else
> @@ -421,6 +464,22 @@ static inline void local_flush_tlb_kernel_page(unsigned long kaddr)
> tlb_op(TLB_V6_U_PAGE, "c8, c7, 1", kaddr);
> tlb_op(TLB_V6_D_PAGE, "c8, c6, 1", kaddr);
> tlb_op(TLB_V6_I_PAGE, "c8, c5, 1", kaddr);
> +
> + if (tlb_flag(TLB_BARRIER)) {
> + dsb();
> + isb();
> + }
> +}
> +
> +static inline void __flush_tlb_kernel_page(unsigned long kaddr)
> +{
> + const unsigned int __tlb_flag = __cpu_tlb_flags;
> +
> + kaddr &= PAGE_MASK;
> +
> + if (tlb_flag(TLB_WB))
> + dsb();
> +
> tlb_op(TLB_V7_UIS_PAGE, "c8, c3, 1", kaddr);
>
> if (tlb_flag(TLB_BARRIER)) {
> diff --git a/arch/arm/kernel/smp_tlb.c b/arch/arm/kernel/smp_tlb.c
> index 9a52a07..cc299b5 100644
> --- a/arch/arm/kernel/smp_tlb.c
> +++ b/arch/arm/kernel/smp_tlb.c
> @@ -135,7 +135,7 @@ void flush_tlb_all(void)
> if (tlb_ops_need_broadcast())
> on_each_cpu(ipi_flush_tlb_all, NULL, 1);
> else
> - local_flush_tlb_all();
> + __flush_tlb_all();
> broadcast_tlb_a15_erratum();
> }
>
> @@ -144,7 +144,7 @@ void flush_tlb_mm(struct mm_struct *mm)
> if (tlb_ops_need_broadcast())
> on_each_cpu_mask(mm_cpumask(mm), ipi_flush_tlb_mm, mm, 1);
> else
> - local_flush_tlb_mm(mm);
> + __flush_tlb_mm(mm);
> broadcast_tlb_mm_a15_erratum(mm);
> }
>
> @@ -157,7 +157,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long uaddr)
> on_each_cpu_mask(mm_cpumask(vma->vm_mm), ipi_flush_tlb_page,
> &ta, 1);
> } else
> - local_flush_tlb_page(vma, uaddr);
> + __flush_tlb_page(vma, uaddr);
> broadcast_tlb_mm_a15_erratum(vma->vm_mm);
> }
>
> @@ -168,7 +168,7 @@ void flush_tlb_kernel_page(unsigned long kaddr)
> ta.ta_start = kaddr;
> on_each_cpu(ipi_flush_tlb_kernel_page, &ta, 1);
> } else
> - local_flush_tlb_kernel_page(kaddr);
> + __flush_tlb_kernel_page(kaddr);
> broadcast_tlb_a15_erratum();
> }
>
> diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
> index 2ac3737..62c1ec5 100644
> --- a/arch/arm/mm/context.c
> +++ b/arch/arm/mm/context.c
> @@ -134,10 +134,7 @@ static void flush_context(unsigned int cpu)
> }
>
> /* Queue a TLB invalidate and flush the I-cache if necessary. */
> - if (!tlb_ops_need_broadcast())
> - cpumask_set_cpu(cpu, &tlb_flush_pending);
> - else
> - cpumask_setall(&tlb_flush_pending);
> + cpumask_setall(&tlb_flush_pending);
>
> if (icache_is_vivt_asid_tagged())
> __flush_icache_all();
> @@ -215,7 +212,6 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
> if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
> local_flush_bp_all();
> local_flush_tlb_all();
> - dummy_flush_tlb_a15_erratum();
> }
>
> atomic64_set(&per_cpu(active_asids, cpu), asid);
>
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