Re: [PATCH] mm/mmap.c: refine data locality of find_vma_prev

From: Wei Yang <richard.weiyang@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richardw.yang@linux.intel.com>,
	Michal Hocko <mhocko@kernel.org>,
	akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/mmap.c: refine data locality of find_vma_prev
Date: Thu, 8 Aug 2019 14:33:36 +0000	[thread overview]
Message-ID: <20190808143336.kgq4f6j5gfixtcb4@master> (raw)
In-Reply-To: <d4aab7f0-b653-8636-b5a7-97d3291f289d@suse.cz>

On Thu, Aug 08, 2019 at 10:49:29AM +0200, Vlastimil Babka wrote:
>On 8/8/19 5:26 AM, Wei Yang wrote:
>> 
>> @@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
>>         if (vma) {
>>                 *pprev = vma->vm_prev;
>>         } else {
>> -               struct rb_node *rb_node = mm->mm_rb.rb_node;
>> -               *pprev = NULL;
>> -               while (rb_node) {
>> -                       *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
>> -                       rb_node = rb_node->rb_right;
>> -               }
>> +               struct rb_node *rb_node = rb_last(&mm->mm_rb);
>> +               *pprev = !rb_node ? NULL :
>> +                        rb_entry(rb_node, struct vm_area_struct, vm_rb);
>>         }
>>         return vma;
>> 
>> Not sure this style would help a little in understanding the code?
>
>Yeah using rb_last() would be nicer than basically repeating its
>implementation, so it's fine as a cleanup without performance implications.
>

Thanks, I would send this version with proper change log.

>>> -- 
>>> Michal Hocko
>>> SUSE Labs
>> 

-- 
Wei Yang
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