Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics

From	Dave Hansen <dave.hansen@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics
Date	2017-07-11 20:30 +0200
Message-ID	<u2854-5KF-21@gated-at.bofh.it> (permalink)
References	<tXTeh-7bI-9@gated-at.bofh.it> <tXTei-7bI-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 06/29/2017 06:44 PM, Huang, Ying wrote:
>  
>  static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
> +static atomic_long_t swapin_readahead_hits_total = ATOMIC_INIT(0);
> +static atomic_long_t swapin_readahead_total = ATOMIC_INIT(0);
>  
>  void show_swap_cache_info(void)
>  {
> @@ -305,8 +307,10 @@ struct page * lookup_swap_cache(swp_entry_t entry)
>  
>  	if (page && likely(!PageTransCompound(page))) {
>  		INC_CACHE_INFO(find_success);
> -		if (TestClearPageReadahead(page))
> +		if (TestClearPageReadahead(page)) {
>  			atomic_inc(&swapin_readahead_hits);
> +			atomic_long_inc(&swapin_readahead_hits_total);
> +		}
>  	}

Adding global atomics that we touch in hot paths seems like poor
future-proofing.  Are we sure we want to do this and not use some of the
nice, fancy, percpu counters that we have?

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Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics Dave Hansen <dave.hansen@intel.com> - 2017-07-11 20:30 +0200
  Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics "Huang\, Ying" <ying.huang@intel.com> - 2017-07-12 04:30 +0200

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