Re: [PATCH] mm/zsmalloc: avoid unnecessary iteration in get_pages_per_zspage()

[Sergey Senozhatsky]

On (05/05/16 13:17), Ganesh Mahendran wrote:
> if we find a zspage with usage == 100%, there is no need to
> try other zspages.

Hello,

well... we iterate there from 0 to 1<<2, which is not awfully
a lot to break it in the middle, and we do this only when we
initialize a new pool (for every size class).

the check is
 - true   15 times
 - false  492 times

so it _sort of_ feels like this new if-condition doesn't
buy us a lot, and most of the time it just sits there with
no particular gain. let's hear from Minchan.

	-ss

> Signed-off-by: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
> ---
>  mm/zsmalloc.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index fda7177..310c7b0 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -765,6 +765,9 @@ static int get_pages_per_zspage(int class_size)
>  		if (usedpc > max_usedpc) {
>  			max_usedpc = usedpc;
>  			max_usedpc_order = i;
> +
> +			if (max_usedpc == 100)
> +				break;
>  		}
>  	}
>  
> -- 
> 1.7.9.5
>