Re: [PATCH 2/3] mm/swapfile: avoid confusing swap cache statistics

[David Hildenbrand]

On 31.05.22 04:55, Miaohe Lin wrote:
> On 2022/5/31 7:04, Andrew Morton wrote:
>> On Fri, 27 May 2022 17:26:25 +0800 Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>>
>>> At swapoff time, we're going to swap in the pages continuously. So calling
>>> lookup_swap_cache would confuse statistics. We should use find_get_page
>>> directly here.
>>
>> Why is the existing behaviour wrong?  swapoff() has to swap stuff in to
>> be able to release the swap device.  Why do you believe that this
>> swapin activity should not be accounted?
> 
> IMHO, statistics, e.g. swap_cache_info.find_success, are used to show the effectiveness
> of the swap cache activity. So they should only reflect the memory accessing activity
> of the user. I think swapoff can't reflect the effectiveness of the swap cache activity
> because it just swaps in pages one by one. Or statistics should reflect all the activity
> of the user including swapoff?

I'm wondering who cares and why?


-- 
Thanks,

David / dhildenb