Re: [PATCH v2 02/11] ARC: send ipi to all cpus sharing task mm in case of page fault

[Vineet Gupta]

On 05/27/2017 11:51 PM, Noam Camus wrote:
> From: Noam Camus <noamca@xxxxxxxxxxxx>
>
> This patch is derived due to performance issue.
> The use case is a page fault that resides on more than the local cpu.
> Trying to broadcast all CPUs results on performance degradation.
> So we try to avoid this by sending only to the relevant CPUs.
>
> Signed-off-by: Noam Camus <noamca@xxxxxxxxxxxx>
> Reviewed-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>

This indeed looks like a nice optimization - do you have any performance numbers 
when say running hackbench or other multi-threaded workloads !

-Vineet

> ---
>   arch/arc/include/asm/cacheflush.h |    3 ++-
>   arch/arc/mm/cache.c               |   12 ++++++++++--
>   arch/arc/mm/tlb.c                 |    2 +-
>   3 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arc/include/asm/cacheflush.h b/arch/arc/include/asm/cacheflush.h
> index fc662f4..716dba1 100644
> --- a/arch/arc/include/asm/cacheflush.h
> +++ b/arch/arc/include/asm/cacheflush.h
> @@ -33,7 +33,8 @@
>   
>   void flush_icache_range(unsigned long kstart, unsigned long kend);
>   void __sync_icache_dcache(phys_addr_t paddr, unsigned long vaddr, int len);
> -void __inv_icache_page(phys_addr_t paddr, unsigned long vaddr);
> +void __inv_icache_page(struct vm_area_struct *vma,
> +		       phys_addr_t paddr, unsigned long vaddr);
>   void __flush_dcache_page(phys_addr_t paddr, unsigned long vaddr);
>   
>   #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
> diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
> index 7d3e79b..e1ea57f 100644
> --- a/arch/arc/mm/cache.c
> +++ b/arch/arc/mm/cache.c
> @@ -934,9 +934,17 @@ void __sync_icache_dcache(phys_addr_t paddr, unsigned long vaddr, int len)
>   }
>   
>   /* wrapper to compile time eliminate alignment checks in flush loop */
> -void __inv_icache_page(phys_addr_t paddr, unsigned long vaddr)
> +void __inv_icache_page(struct vm_area_struct *vma,
> +		       phys_addr_t paddr, unsigned long vaddr)
>   {
> -	__ic_line_inv_vaddr(paddr, vaddr, PAGE_SIZE);
> +	struct ic_inv_args ic_inv = {
> +		.paddr	= paddr,
> +		.vaddr	= vaddr,
> +		.sz	= PAGE_SIZE
> +	};
> +
> +	on_each_cpu_mask(mm_cpumask(vma->vm_mm),
> +			 __ic_line_inv_vaddr_helper, &ic_inv, 1);
>   }
>   
>   /*
> diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
> index c5e70d8..a095608 100644
> --- a/arch/arc/mm/tlb.c
> +++ b/arch/arc/mm/tlb.c
> @@ -626,7 +626,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr_unaligned,
>   
>   			/* invalidate any existing icache lines (U-mapping) */
>   			if (vma->vm_flags & VM_EXEC)
> -				__inv_icache_page(paddr, vaddr);
> +				__inv_icache_page(vma, paddr, vaddr);
>   		}
>   	}
>   }