linux-kernel - Re: [PATCH] mm/cma: print total and used count in cma

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Message-ID: <755ff53a-2727-4993-92b4-95be668f3b67@redhat.com>
Date: Fri, 27 Sep 2024 14:30:18 +0200
From: David Hildenbrand <david@...hat.com>
To: Xiang Gao <gxxa03070307@...il.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 gaoxiang17 <gaoxiang17@...omi.com>
Subject: Re: [PATCH] mm/cma: print total and used count in cma_alloc()

On 26.09.24 14:00, Xiang Gao wrote:
> From: gaoxiang17 <gaoxiang17@...omi.com>
> 
> before:
> [   24.407814] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)
> [   24.413397] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)
> [   24.415886] cma: cma_alloc(cma (____ptrval____), name: reserved, count 1, align 0)
> 
> after:
> [   24.097989] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 64, request count 1, align 0)
> [   24.104260] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 65, request count 1, align 0)
> [   24.107504] cma: cma_alloc(cma (____ptrval____), name: reserved, total count 16384, used count: 66, request count 1, align 0)
> 
> Signed-off-by: gaoxiang17 <gaoxiang17@...omi.com>
> ---
>   mm/cma.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 2d9fae939283..fc35a86aa82f 100644
> --- 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)

I would call it "cma_get_used_pages()"

> +{
> +	unsigned long used;
> +
> +	spin_lock_irq(&cma->lock);
> +	used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma));
> +	spin_unlock_irq(&cma->lock);
> +
> +	return used << cma->order_per_bit;
> +}
> +
>   static struct page *__cma_alloc(struct cma *cma, unsigned long count,
>   				unsigned int align, gfp_t gfp)
>   {
> @@ -420,8 +431,8 @@ static 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__,

I would suggest dropping the "count", or using "pages" instead. Also, 
inconsistent usage of ":".

Either:

pr_debug("%s(cma %p, name: %s, total: %lu, used: %lu, requested: %lu, ..."

or

pr_debug("%s(cma %p, name: %s, total pages: %lu, used pages: %lu, 
requested pages: %lu, ..."

> +		(void *)cma, cma->name, cma->count, cma_get_used(cma), count, align);
>   
>   	if (!count)
>   		return page;


-- 
Cheers,

David / dhildenb