linux-kernel - Re: [PATCH v6 6/6] mm/vmscan: restore active/inactive ratio for anonymous LRU

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Date:   Thu, 2 Jul 2020 15:45:22 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     js1304@...il.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>, kernel-team@....com,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v6 6/6] mm/vmscan: restore active/inactive ratio for
 anonymous LRU

On 6/17/20 7:26 AM, js1304@...il.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> Now, workingset detection is implemented for anonymous LRU.
> We don't have to worry about the misfound for workingset due to
> the ratio of active/inactive. Let's restore the ratio.

How about:

Now that workingset detection is implemented for anonymous LRU, we don't need
large inactive list to allow detecting frequently accessed pages before they are
reclaimed, anymore. This effectively reverts the temporary measure put in by
commit "mm/vmscan: make active/inactive ratio as 1:1 for anon lru".

> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!
I still hope Matthew can review updated patch 4/6 (I'm not really familiar with
proper xarray handling), and Johannes patch 5/6.

And then we just need a nice Documentation file describing how reclaim really
works after all the recent changes :)

Vlastimil

> ---
>  mm/vmscan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index eb02d18..ec77691 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2211,7 +2211,7 @@ static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
>  	active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
>  
>  	gb = (inactive + active) >> (30 - PAGE_SHIFT);
> -	if (gb && is_file_lru(inactive_lru))
> +	if (gb)
>  		inactive_ratio = int_sqrt(10 * gb);
>  	else
>  		inactive_ratio = 1;
>