linux-kernel - Re: [PATCH 5/5] mm/page_alloc: improve memmap_pages and dma

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Date:   Tue, 25 May 2021 10:01:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Dong Aisheng <aisheng.dong@....com>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, dongas86@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 5/5] mm/page_alloc: improve memmap_pages and dma_reserve
 dbg msg

On 17.05.21 13:20, Dong Aisheng wrote:
> Make debug message more accurately.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> ---
>   mm/page_alloc.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3100fcb08500..16f494352f58 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7263,14 +7263,15 @@ static void __init free_area_init_core(struct pglist_data *pgdat)
>   					pr_debug("  %s zone: %lu pages used for memmap\n",
>   						 zone_names[j], memmap_pages);
>   			} else
> -				pr_warn("  %s zone: %lu pages exceeds freesize %lu\n",
> +				pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
>   					zone_names[j], memmap_pages, freesize);
>   		}
>   
>   		/* Account for reserved pages */
>   		if (j == 0 && freesize > dma_reserve) {
>   			freesize -= dma_reserve;
> -			pr_debug("  %s zone: %lu pages reserved\n", zone_names[0], dma_reserve);
> +			pr_debug("  %s zone: %lu pages reserved for dma\n",
> +				 zone_names[0], dma_reserve);

... which is not really correct I think. See the comment above 
set_dma_reserve(). It's called dma_reserve because it involves the first 
zone -- where many unfreeable allocations like the kernel image end up.

Memory is not reserved for dma purposes ... and the zone name should be 
sufficient.

-- 
Thanks,

David / dhildenb