Messages in this thread | | | Date | Sun, 28 Sep 2008 21:34:36 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH 3/3] x86/iommu: use __GFP_ZERO instead of memset for GART |
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On Sat, Sep 27, 2008 at 08:18:55PM +0200, Ingo Molnar wrote: > > another thing: > > How hard would it be to add an CONFIG_IOMMU_DEBUG option that forces as > many DMA requests to go via the IOMMU as possible? > > This slows things down of course so it's only for debugging - but it > also makes sure that we utilize the IOMMU code to the maximum - which is > not normally the case. > > Would be nice to have it .config driven (default-disabled), so that > -tip's randconfig testing can stumble upon it every now and then. I've > got GART test-systems - this way we could find certain types of IOMMU > breakages sooner.
For AMD IOMMU I disabled the round-robin allocator to stress-test the code. This means that the address allocation bitmap is always traversed from the first bit. In consequence the TLB flushing is stressed a lot (both in hardware and software) because the same DMA addresses are used again and again. For testing I hardcoded it into the driver but I can also make it depend on CONFIG_IOMMU_DEBUG.
Joerg
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