Hello,
On Wed, Apr 07, 2021 at 08:57:35PM -0700, Roman Gushchin wrote:
> Factor out the pcpu_check_chunk_hint() helper, which will be useful
> in the future. The new function checks if the allocation can likely
> fit the given chunk.
>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> ---
> mm/percpu.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index e20119668c42..357fd6994278 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -306,6 +306,26 @@ static unsigned long pcpu_block_off_to_off(int index, int off)
> return index * PCPU_BITMAP_BLOCK_BITS + off;
> }
>
> +/**
> + * pcpu_check_chunk_hint - check that allocation can fit a chunk
> + * @chunk_md: chunk's block
nit for consistency: @block: block of interest
> + * @bits: size of request in allocation units
> + * @align: alignment of area (max PAGE_SIZE)
> + *
> + * Check to see if the allocation can fit in the chunk's contig hint.
> + * This is an optimization to prevent scanning by assuming if it
> + * cannot fit in the global hint, there is memory pressure and creating
> + * a new chunk would happen soon.
> + */
It occurred to me, That I converged block_md and chunk_md to be the same
object as 1 is just a degenerative case of the other. Can we rename this
to be pcpu_check_block_hint() and have it take in pcpu_block_md?
> +static bool pcpu_check_chunk_hint(struct pcpu_block_md *chunk_md, int bits,
> + size_t align)
> +{
> + int bit_off = ALIGN(chunk_md->contig_hint_start, align) -
> + chunk_md->contig_hint_start;
> +
> + return bit_off + bits <= chunk_md->contig_hint;
> +}
> +
> /*
> * pcpu_next_hint - determine which hint to use
> * @block: block of interest
> @@ -1065,15 +1085,7 @@ static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
> struct pcpu_block_md *chunk_md = &chunk->chunk_md;
> int bit_off, bits, next_off;
>
> - /*
> - * Check to see if the allocation can fit in the chunk's contig hint.
> - * This is an optimization to prevent scanning by assuming if it
> - * cannot fit in the global hint, there is memory pressure and creating
> - * a new chunk would happen soon.
> - */
> - bit_off = ALIGN(chunk_md->contig_hint_start, align) -
> - chunk_md->contig_hint_start;
> - if (bit_off + alloc_bits > chunk_md->contig_hint)
> + if (!pcpu_check_chunk_hint(chunk_md, alloc_bits, align))
> return -1;
>
> bit_off = pcpu_next_hint(chunk_md, alloc_bits);
> --
> 2.30.2
>
Thanks,
Dennis
