linux-kernel - Re: [PATCH 1/3] x86: mm: Clean up inconsistencies when flushing TLB ranges

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Date:	Thu, 12 Dec 2013 21:59:33 +0800
From:	Alex Shi <alex.shi@...aro.org>
To:	Mel Gorman <mgorman@...e.de>
CC:	H Peter Anvin <hpa@...or.com>, Linux-X86 <x86@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] x86: mm: Clean up inconsistencies when flushing TLB
 ranges

On 12/12/2013 07:55 PM, Mel Gorman wrote:
> NR_TLB_LOCAL_FLUSH_ALL is not always accounted for correctly and the
> comparison with total_vm is done before taking tlb_flushall_shift into
> account. Clean it up.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Alex Shi
> ---
>  arch/x86/mm/tlb.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index ae699b3..09b8cb8 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -189,6 +189,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
>  {
>  	unsigned long addr;
>  	unsigned act_entries, tlb_entries = 0;
> +	unsigned long nr_base_pages;
>  
>  	preempt_disable();
>  	if (current->active_mm != mm)
> @@ -210,18 +211,17 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
>  		tlb_entries = tlb_lli_4k[ENTRIES];
>  	else
>  		tlb_entries = tlb_lld_4k[ENTRIES];
> +
>  	/* Assume all of TLB entries was occupied by this task */

the benchmark break this assumption?
> -	act_entries = mm->total_vm > tlb_entries ? tlb_entries : mm->total_vm;
> +	act_entries = tlb_entries >> tlb_flushall_shift;
> +	act_entries = mm->total_vm > act_entries ? act_entries : mm->total_vm;
> +	nr_base_pages = (end - start) >> PAGE_SHIFT;
>  
>  	/* tlb_flushall_shift is on balance point, details in commit log */
> -	if ((end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift) {
> +	if (nr_base_pages > act_entries || has_large_page(mm, start, end)) {
>  		count_vm_event(NR_TLB_LOCAL_FLUSH_ALL);
>  		local_flush_tlb();
>  	} else {
> -		if (has_large_page(mm, start, end)) {
> -			local_flush_tlb();
> -			goto flush_all;
> -		}
>  		/* flush range by one by one 'invlpg' */
>  		for (addr = start; addr < end;	addr += PAGE_SIZE) {
>  			count_vm_event(NR_TLB_LOCAL_FLUSH_ONE);
> 


-- 
Thanks
    Alex
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