On 15/08/2019 14:35, Christoph Hellwig wrote:
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:

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.

FWIW, the cacheline tracking entries are a separate thing from the dma-debug entries that I rejigged - judging by those numbers there should still be plenty of free dma-debug entries, but for some reason it has failed to extend the radix tree :/


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