linux-kernel - Re: [PATCH] dma-debug: Make things less spammy under memory pressure

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Date:   Tue, 31 May 2022 23:00:18 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Rob Clark <robdclark@...il.com>, linux-kernel@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "open list:DMA MAPPING HELPERS" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH] dma-debug: Make things less spammy under memory pressure

On 2022-05-31 22:51, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Ratelimit the error msg to avoid flooding the console.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>   kernel/dma/debug.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
> index f8ff598596b8..683966f0247b 100644
> --- a/kernel/dma/debug.c
> +++ b/kernel/dma/debug.c
> @@ -564,7 +564,7 @@ static void add_dma_entry(struct dma_debug_entry *entry, unsigned long attrs)
>   
>   	rc = active_cacheline_insert(entry);
>   	if (rc == -ENOMEM) {
> -		pr_err("cacheline tracking ENOMEM, dma-debug disabled\n");
> +		pr_err_ratelimited("cacheline tracking ENOMEM, dma-debug disabled\n");
>   		global_disable = true;

Given that it's supposed to disable itself entirely if it ever gets 
here, just how spammy is it exactly?

Thanks,
Robin.

>   	} else if (rc == -EEXIST && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
>   		err_printk(entry->dev, entry,