Re: DMA-API: cacheline tracking ENOMEM, dma-debug disabled due to nouveau ?
From: Daniel Vetter
Date: Fri Aug 16 2019 - 14:45:26 EST
On Fri, Aug 16, 2019 at 4:31 PM Corentin Labbe
> 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.
> Note that it never go down and when I terminate my X session, it stays the same.
> So without any "real" GPU work, does it is still normal to have so many active mapping ?
Might just be the dma_alloc cache. It should go down under memory
pressure I think. Otherwise might also be a leak.
> For example, when doing some transfer, the ahci mapping number changes and then always go down to 6.
gpu drivers tend to cache everything, all the time ...
Software Engineer, Intel Corporation
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