From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Fri, 14 Sep 2018 13:48:59 +0100 Subject: [PATCH v2 0/3] iommu: Avoid DMA ops domain refcount contention In-Reply-To: References: Message-ID: <20180914124858.GA4010@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Robin, On Wed, Sep 12, 2018 at 04:24:11PM +0100, Robin Murphy wrote: > John raised the issue[1] that we have some unnecessary refcount contention > in the DMA ops path which shows scalability problems now that we have more > real high-performance hardware using iommu-dma. The x86 IOMMU drivers are > sidestepping this by stashing domain references in archdata, but since > that's not very nice for architecture-agnostic code, I think it's time to > look at a generic API-level solution. > > These are a couple of quick patches based on the idea I had back when > first implementing iommu-dma, but didn't have any way to justify at the > time. However, the reports of 10-25% better networking performance on v1 > suggest that it's very worthwhile (and far more significant than I ever > would have guessed). > > As far as merging goes, I don't mind at all whether this goes via IOMMU, > or via dma-mapping provided Joerg's happy to ack it. I think it makes most sense for Joerg to take this series via his tree. Anyway, I've been running them on my TX2 box and things are happy enough, so: Tested-by: Will Deacon Will