Andrew Morton <a...@linux-foundation.org> writes:

> On Mon,  7 Aug 2017 13:40:34 +0800 "Huang, Ying" <ying.hu...@intel.com> wrote:
>
>> From: Huang Ying <ying.hu...@intel.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 */
> _

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