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Subject: Re: [PATCH 1/2] mm: use sc->priority for slab shrink targets
References: <1503430539-2878-1-git-send-email-jbacik@fb.com>
From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <a6a68b0b-4138-2563-fa53-ad8406dc6e34@virtuozzo.com>
Date: Thu, 24 Aug 2017 17:29:59 +0300
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Sender: owner-linux-mm@kvack.org
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To: josef@toxicpanda.com, minchan@kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, riel@redhat.com, akpm@linux-foundation.org, david@fromorbit.com, kernel-team@fb.com
Cc: Josef Bacik <jbacik@fb.com>



On 08/22/2017 10:35 PM, josef@toxicpanda.com wrote:
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -306,9 +306,7 @@ EXPORT_SYMBOL(unregister_shrinker);
>  #define SHRINK_BATCH 128
>  
>  static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> -				    struct shrinker *shrinker,
> -				    unsigned long nr_scanned,
> -				    unsigned long nr_eligible)
> +				    struct shrinker *shrinker, int priority)
>  {
>  	unsigned long freed = 0;
>  	unsigned long long delta;
> @@ -333,9 +331,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
>  	nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
>  
>  	total_scan = nr;
> -	delta = (4 * nr_scanned) / shrinker->seeks;
> -	delta *= freeable;
> -	do_div(delta, nr_eligible + 1);
> +	delta = freeable >> priority;
> +	delta = (4 * freeable) / shrinker->seeks;

Something is wrong. The first line does nothing.


>  	total_scan += delta;
>  	if (total_scan < 0) {
>  		pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",

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