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Subject: Re: [RFC 2/3] mm/slub: sort objects in cache by frequency of stack
 trace
To:     glittao@gmail.com, cl@linux.com, penberg@kernel.org,
        rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        faiyazm@codeaurora.org
References: <20210521121127.24653-1-glittao@gmail.com>
 <20210521121127.24653-2-glittao@gmail.com>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <c9b88ab1-42dc-1198-4ad1-e9a980d4a6bf@suse.cz>
Date:   Wed, 26 May 2021 16:06:39 +0200
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On 5/21/21 2:11 PM, glittao@gmail.com wrote:
> From: Oliver Glitta <glittao@gmail.com>
> 
> Sort objects in slub cache by the frequency of stack trace used
> in object location in alloc_calls and free_calls implementation
> in debugfs. Most frequently used stack traces will be the first.

That will make it much more convenient.

> Signed-off-by: Oliver Glitta <glittao@gmail.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/slub.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index d5ed6ed7d68b..247983d647cd 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -37,6 +37,7 @@
>  #include <linux/memcontrol.h>
>  #include <linux/random.h>
>  #include <kunit/test.h>
> +#include <linux/sort.h>
>  
>  #include <linux/debugfs.h>
>  #include <trace/events/kmem.h>
> @@ -5893,6 +5894,17 @@ static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>  	return NULL;
>  }
>  
> +static int cmp_loc_by_count(const void *a, const void *b, const void *data)
> +{
> +	struct location *loc1 = (struct location *)a;
> +	struct location *loc2 = (struct location *)b;
> +
> +	if (loc1->count > loc2->count)
> +		return -1;
> +	else
> +		return 1;
> +}
> +
>  static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
>  {
>  	struct kmem_cache_node *n;
> @@ -5944,6 +5956,11 @@ static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
>  				process_slab(&t, s, page, alloc);
>  			spin_unlock_irqrestore(&n->list_lock, flags);
>  		}
> +
> +		/* Sort locations by count */
> +		sort_r(t.loc, t.count, sizeof(struct location),
> +				cmp_loc_by_count, NULL, NULL);
> +
>  	}
>  
>  	if (*ppos < t.count) {
>