linux-kernel - Re: [RFC 4/4] dma-debug: Make leak-like behaviour apparent

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Message-ID: <20181204143106.GD2767@lst.de>
Date:   Tue, 4 Dec 2018 15:31:06 +0100
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     hch@....de, m.szyprowski@...sung.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        cai@....us, salil.mehta@...wei.com, john.garry@...wei.com
Subject: Re: [RFC 4/4] dma-debug: Make leak-like behaviour apparent

On Mon, Dec 03, 2018 at 05:28:09PM +0000, Robin Murphy wrote:
> Now that we can dynamically allocate DMA debug entries to cope with
> drivers maintaining excessively large numbers of live mappings, a driver
> which *does* actually have a bug leaking mappings (and is not unloaded)
> will no longer trigger the "DMA-API: debugging out of memory - disabling"
> message until it gets to actual kernel OOM conditions, which means it
> could go unnoticed for a while. To that end, let's inform the user each
> time the pool has grown to a multiple of its initial size, which should
> make it apparent that they either have a leak or might want to increase
> the preallocation size.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
> 
> Tagging this one as RFC since people might think it's silly.

I think finding out the numbers is useful, but I'm a little worried
about claiming a possible leak.  Maybe we just need to print a log message
for each new power of 2 of entries reached?