Re: [PATCH v1 1/5] percpu: return number of released bytes from pcpu_free_area()

Dennis Zhou
2020-06-05T19:44:49Z

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