Messages in this thread | | | Date | Fri, 11 Nov 2011 14:24:11 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH v4 2/7] iommu/core: split mapping to page sizes as supported by the hardware |
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On Thu, Nov 10, 2011 at 01:12:00PM -0800, Stepan Moskovchenko wrote: > I have been experimenting with an iommu_map_range call, which maps a > given scatterlist of discontiguous physical pages into a contiguous > virtual region at a given IOVA. This has some performance advantages > over just calling iommu_map iteratively. First, it reduces the > amount of table walking / calculation needed for mapping each page, > given how you know that all the pages will be mapped into a single > virtually-contiguous region (so in most cases, the first-level table > calculation can be reused). Second, it allows one to defer the TLB > (and sometimes cache) maintenance operations until the entire > scatterlist has been mapped, rather than doing a TLB invalidate > after mapping each page, as would have been the case if iommu_map > were just being called from within a loop. Granted, just using > iommu_map many times may be acceptable on the slow path, but I have > seen significant performance gains when using this approach on the > fast path.
Yes, from a performance point-of-view that makes sense, as an addition to the existing iommu_map interface. Are the pages in the list allowed to have different page-sizes?
Joerg
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