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Date:   Fri, 5 Jun 2020 19:44:43 +0000
From:   Dennis Zhou <dennis@kernel.org>
To:     Roman Gushchin <guro@fb.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>, linux-mm@kvack.org,
        kernel-team@fb.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 1/5] percpu: return number of released bytes from
 pcpu_free_area()
Message-ID: <20200605194443.GA224745@google.com>
References: <20200528232508.1132382-1-guro@fb.com>
 <20200528232508.1132382-2-guro@fb.com>
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On Thu, May 28, 2020 at 04:25:04PM -0700, Roman Gushchin wrote:
> To implement accounting of percpu memory we need the information
> about the size of freed object. Return it from pcpu_free_area().
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> ---
>  mm/percpu.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 696367b18222..aa36b78d45a6 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -1211,11 +1211,14 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
>   *
>   * This function determines the size of an allocation to free using
>   * the boundary bitmap and clears the allocation map.
> + *
> + * RETURNS:
> + * Number of freed bytes.
>   */
> -static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
> +static int pcpu_free_area(struct pcpu_chunk *chunk, int off)
>  {
>  	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
> -	int bit_off, bits, end, oslot;
> +	int bit_off, bits, end, oslot, freed;
>  
>  	lockdep_assert_held(&pcpu_lock);
>  	pcpu_stats_area_dealloc(chunk);
> @@ -1230,8 +1233,10 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
>  	bits = end - bit_off;
>  	bitmap_clear(chunk->alloc_map, bit_off, bits);
>  
> +	freed = bits * PCPU_MIN_ALLOC_SIZE;
> +
>  	/* update metadata */
> -	chunk->free_bytes += bits * PCPU_MIN_ALLOC_SIZE;
> +	chunk->free_bytes += freed;
>  
>  	/* update first free bit */
>  	chunk_md->first_free = min(chunk_md->first_free, bit_off);
> @@ -1239,6 +1244,8 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
>  	pcpu_block_update_hint_free(chunk, bit_off, bits);
>  
>  	pcpu_chunk_relocate(chunk, oslot);
> +
> +	return freed;
>  }
>  
>  static void pcpu_init_md_block(struct pcpu_block_md *block, int nr_bits)
> -- 
> 2.25.4
> 

Sorry for the delay.

Acked-by: Dennis Zhou <dennis@kernel.org>

What's the status of the depending patches? It might be easiest to have
Andrew pick these up once the depending patch series is settled.

Thanks,
Dennis