Messages in this thread | | | Date | Sun, 4 Nov 2018 07:50:01 -0800 | From | Christoph Hellwig <> | Subject | Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist |
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On Thu, Nov 01, 2018 at 02:35:00PM -0700, Nicolin Chen wrote: > The __GFP_ZERO will be passed down to the generic page allocation > routine which zeros everything page by page. This is safe to be a > generic way but not efficient for iommu allocation that organizes > contiguous pages using scatterlist. > > So this changes drops __GFP_ZERO from the flag, and adds a manual > memset after page/sg allocations, using the length of scatterlist. > > My test result of a 2.5MB size allocation shows iommu_dma_alloc() > takes 46% less time, reduced from averagely 925 usec to 500 usec.
And in what case does dma_alloc_* performance even matter?
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