linux-kernel - Re: [PATCH] mm/cma.c: To better understand cma area during debugging, add total and used count logs to in cma

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Message-Id: <20240924172719.a486793abd66643d9938081f@linux-foundation.org>
Date: Tue, 24 Sep 2024 17:27:19 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Xiang Gao <gxxa03070307@...il.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, gaoxiang17
 <gaoxiang17@...omi.com>
Subject: Re: [PATCH] mm/cma.c: To better understand cma area during
 debugging, add total and used count logs to in cma_alloc

On Wed, 18 Sep 2024 20:43:25 +0800 Xiang Gao <gxxa03070307@...il.com> wrote:

> From: gaoxiang17 <gaoxiang17@...omi.com>
> 
> [   24.225125] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 64, request count 1, align 0)
> [   24.231963] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 65, request count 1, align 0)
> [   24.235712] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 66, request count 1, align 0)
> 

Providing before-and-after output would make the proposal more easily
understood.

> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -403,6 +403,17 @@ static void cma_debug_show_areas(struct cma *cma)
>  	spin_unlock_irq(&cma->lock);
>  }
>  
> +static unsigned long cma_get_used(struct cma *cma)
> +{
> +	unsigned long used;
> +
> +	spin_lock_irq(&cma->lock);
> +	used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma));

Is the (int) cast needed?

> +	spin_unlock_irq(&cma->lock);
> +
> +	return (unsigned long)used << cma->order_per_bit;

Is the (unsigned long) bast needed?

> +}
> +
>  /**
>   * cma_alloc() - allocate pages from contiguous area
>   * @cma:   Contiguous memory region for which the allocation is performed.
> @@ -430,8 +441,8 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
>  	if (!cma || !cma->count || !cma->bitmap)
>  		return page;
>  
> -	pr_debug("%s(cma %p, name: %s, count %lu, align %d)\n", __func__,
> -		(void *)cma, cma->name, count, align);
> +	pr_debug("%s(cma %p, name: %s, total count %lu, used count: %lu, request count %lu, align %d)\n", __func__,
> +		(void *)cma, cma->name, cma->count, cma_get_used(cma), count, align);
>  
>  	if (!count)
>  		return page;
> -- 
> 2.34.1