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From: Dennis Zhou <dennis@kernel.org>
To: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 5/6] percpu: factor out pcpu_check_chunk_hint()
Date: Fri, 16 Apr 2021 21:15:25 +0000	[thread overview]
Message-ID: <YHn+beQ8QRpm8WqU@google.com> (raw)
In-Reply-To: <20210408035736.883861-6-guro@fb.com>

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@fb.com>
> ---
>  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

  reply	other threads:[~2021-04-16 21:15 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08  3:57 [PATCH v3 0/6] percpu: partial chunk depopulation Roman Gushchin
2021-04-08  3:57 ` [PATCH v3 1/6] percpu: fix a comment about the chunks ordering Roman Gushchin
2021-04-16 21:06   ` Dennis Zhou
2021-04-08  3:57 ` [PATCH v3 2/6] percpu: split __pcpu_balance_workfn() Roman Gushchin
2021-04-16 21:06   ` Dennis Zhou
2021-04-08  3:57 ` [PATCH v3 3/6] percpu: make pcpu_nr_empty_pop_pages per chunk type Roman Gushchin
2021-04-16 21:08   ` Dennis Zhou
2021-04-08  3:57 ` [PATCH v3 4/6] percpu: generalize pcpu_balance_populated() Roman Gushchin
2021-04-16 21:09   ` Dennis Zhou
2021-04-08  3:57 ` [PATCH v3 5/6] percpu: factor out pcpu_check_chunk_hint() Roman Gushchin
2021-04-16 21:15   ` Dennis Zhou [this message]
2021-04-08  3:57 ` [PATCH v3 6/6] percpu: implement partial chunk depopulation Roman Gushchin
2021-04-16 12:56 ` [PATCH v3 0/6] percpu: " Pratik Sampat
2021-04-16 14:18   ` Dennis Zhou
2021-04-16 15:28     ` Pratik Sampat
2021-04-16 17:13       ` Roman Gushchin
2021-04-16 18:27         ` Pratik Sampat
2021-04-16 18:34           ` Roman Gushchin
2021-04-16 18:41             ` Pratik Sampat
2021-04-16 19:09               ` Roman Gushchin
2021-04-16 19:44                 ` Pratik Sampat
2021-04-16 20:03                   ` Roman Gushchin
2021-04-17  7:08                     ` Pratik Sampat
2021-04-16 21:47                   ` Dennis Zhou
2021-04-17  7:14                     ` Pratik Sampat
2021-04-16 16:21     ` Roman Gushchin

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