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Date:   Thu, 15 Aug 2019 15:35:54 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Corentin Labbe <clabbe.montjoie@gmail.com>, bskeggs@redhat.com,
        airlied@linux.ie, hch@lst.de, m.szyprowski@samsung.com,
        robin.murphy@arm.com, dri-devel@lists.freedesktop.org,
        nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        iommu@lists.linux-foundation.org
Subject: Re: DMA-API: cacheline tracking ENOMEM, dma-debug disabled due to
 nouveau ?
Message-ID: <20190815133554.GE12036@lst.de>
References: <20190814145033.GA11190@Red> <20190814174927.GT7444@phenom.ffwll.local>
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On Wed, Aug 14, 2019 at 07:49:27PM +0200, Daniel Vetter wrote:
> On Wed, Aug 14, 2019 at 04:50:33PM +0200, Corentin Labbe wrote:
> > Hello
> > 
> > Since lot of release (at least since 4.19), I hit the following error message:
> > DMA-API: cacheline tracking ENOMEM, dma-debug disabled
> > 
> > After hitting that, I try to check who is creating so many DMA mapping and see:
> > cat /sys/kernel/debug/dma-api/dump | cut -d' ' -f2 | sort | uniq -c
> >       6 ahci
> >     257 e1000e
> >       6 ehci-pci
> >    5891 nouveau
> >      24 uhci_hcd
> > 
> > Does nouveau having this high number of DMA mapping is normal ?
> 
> Yeah seems perfectly fine for a gpu.

That is a lot and apparently overwhelm the dma-debug tracking.  Robin
rewrote this code in Linux 4.21 to work a little better, so I'm curious
why this might have changes in 4.19, as dma-debug did not change at
all there.