RE: [PATCH 10/12] percpu: make pcpu_block_md generic

[Peng Fan]

> -----Original Message-----
> From: owner-linux-mm@xxxxxxxxx [mailto:owner-linux-mm@xxxxxxxxx] On
> Behalf Of Dennis Zhou
> Sent: 2019年2月28日 10:19
> To: Dennis Zhou <dennis@xxxxxxxxxx>; Tejun Heo <tj@xxxxxxxxxx>; Christoph
> Lameter <cl@xxxxxxxxx>
> Cc: Vlad Buslov <vladbu@xxxxxxxxxxxx>; kernel-team@xxxxxx;
> linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH 10/12] percpu: make pcpu_block_md generic
> 
> In reality, a chunk is just a block covering a larger number of bits.
> The hints themselves are one in the same. Rather than maintaining the hints
> separately, first introduce nr_bits to genericize
> pcpu_block_update() to correctly maintain block->right_free. The next patch
> will convert chunk hints to be managed as a pcpu_block_md.
> 
> Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>
> ---
>  mm/percpu-internal.h |  1 +
>  mm/percpu.c          | 20 +++++++++++++-------
>  2 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index
> ec58b244545d..119bd1119aa7 100644
> --- a/mm/percpu-internal.h
> +++ b/mm/percpu-internal.h
> @@ -28,6 +28,7 @@ struct pcpu_block_md {
>  	int                     right_free;     /* size of free space along
>  						   the right side of the block */
>  	int                     first_free;     /* block position of first free
> */
> +	int			nr_bits;	/* total bits responsible for */
>  };
> 
>  struct pcpu_chunk {
> diff --git a/mm/percpu.c b/mm/percpu.c
> index e51c151ed692..7cdf14c242de 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -658,7 +658,7 @@ static void pcpu_block_update(struct pcpu_block_md
> *block, int start, int end)
>  	if (start == 0)
>  		block->left_free = contig;
> 
> -	if (end == PCPU_BITMAP_BLOCK_BITS)
> +	if (end == block->nr_bits)
>  		block->right_free = contig;
> 
>  	if (contig > block->contig_hint) {
> @@ -1271,18 +1271,24 @@ static void pcpu_free_area(struct pcpu_chunk
> *chunk, int off)
>  	pcpu_chunk_relocate(chunk, oslot);
>  }
> 
> +static void pcpu_init_md_block(struct pcpu_block_md *block, int
> +nr_bits) {
> +	block->scan_hint = 0;
> +	block->contig_hint = nr_bits;
> +	block->left_free = nr_bits;
> +	block->right_free = nr_bits;
> +	block->first_free = 0;
> +	block->nr_bits = nr_bits;
> +}
> +
>  static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)  {
>  	struct pcpu_block_md *md_block;
> 
>  	for (md_block = chunk->md_blocks;
>  	     md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
> -	     md_block++) {
> -		md_block->scan_hint = 0;
> -		md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
> -		md_block->left_free = PCPU_BITMAP_BLOCK_BITS;
> -		md_block->right_free = PCPU_BITMAP_BLOCK_BITS;
> -	}
> +	     md_block++)
> +		pcpu_init_md_block(md_block, PCPU_BITMAP_BLOCK_BITS);
>  }

Reviewed-by: Peng Fan <peng.fan@xxxxxxx>

> 
>  /**
> --
> 2.17.1