From: Sowmini Varadhan <sowmini.varad...@oracle.com> Date: Sun, 22 Mar 2015 15:27:26 -0400
> That leaves only the odd iommu_flushall() hook, I'm trying > to find the history behind that (needed for sun4u platforms, > afaik, and not sure if there are other ways to achieve this). In order to elide the IOMMU flush as much as possible, I implemnented a scheme for sun4u wherein we always allocated from low IOMMU addresses to high IOMMU addresses. In this regime, we only need to flush the IOMMU when we rolled over back to low IOMMU addresses during an allocation. It made a noticable difference in performance. Unfortunately, with sun4v and the hypervisor, I'm not allowed to control when the IOMMU flush happens, it has to occur on every single IOMMU mapping change. So this optimization was no longer possible there. Anyways, that's the history behind it. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
