linux-kernel - Re: [PATCH -mm -v4 1/5] mm, swap: Add swap readahead hit statistics

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Date:   Thu, 10 Aug 2017 07:17:30 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Huang\, Ying" <ying.huang@...el.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>, Shaohua Li <shli@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Tim Chen <tim.c.chen@...el.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH -mm -v4 1/5] mm, swap: Add swap readahead hit statistics

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Mon,  7 Aug 2017 13:40:34 +0800 "Huang, Ying" <ying.huang@...el.com> wrote:
>
>> From: Huang Ying <ying.huang@...el.com>
>> 
>> The statistics for total readahead pages and total readahead hits are
>> recorded and exported via the following sysfs interface.
>> 
>> /sys/kernel/mm/swap/ra_hits
>> /sys/kernel/mm/swap/ra_total
>> 
>> With them, the efficiency of the swap readahead could be measured, so
>> that the swap readahead algorithm and parameters could be tuned
>> accordingly.
>> 
>> ...
>>
>> --- a/include/linux/vm_event_item.h
>> +++ b/include/linux/vm_event_item.h
>> @@ -106,6 +106,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>>  		VMACACHE_FIND_HITS,
>>  		VMACACHE_FULL_FLUSHES,
>>  #endif
>> +		SWAP_RA,
>> +		SWAP_RA_HIT,
>>  		NR_VM_EVENT_ITEMS
>>  };
>
> swap_state.o isn't even compiled if CONFIG_SWAP=n so there doesn't seem
> much point in displaying these?

Oh, Yes!  Thanks for pointing this out.

Best Regards,
Huang, Ying

> --- a/include/linux/vm_event_item.h~mm-swap-add-swap-readahead-hit-statistics-fix
> +++ a/include/linux/vm_event_item.h
> @@ -106,8 +106,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
>  		VMACACHE_FIND_HITS,
>  		VMACACHE_FULL_FLUSHES,
>  #endif
> +#ifdef CONFIG_SWAP
>  		SWAP_RA,
>  		SWAP_RA_HIT,
> +#endif
>  		NR_VM_EVENT_ITEMS
>  };
>  
> --- a/mm/vmstat.c~mm-swap-add-swap-readahead-hit-statistics-fix
> +++ a/mm/vmstat.c
> @@ -1098,9 +1098,10 @@ const char * const vmstat_text[] = {
>  	"vmacache_find_hits",
>  	"vmacache_full_flushes",
>  #endif
> -
> +#ifdef CONFIG_SWAP
>  	"swap_ra",
>  	"swap_ra_hit",
> +#endif
>  #endif /* CONFIG_VM_EVENTS_COUNTERS */
>  };
>  #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA */
> _