Messages in this thread |  | | | Date | Tue, 22 Mar 2011 13:15:52 -0700 (PDT) | | Subject | Re: [PATCH 0/6] get rid of on-stack dma buffers | | From | David Miller <> |
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From: James Bottomley <James.Bottomley@HansenPartnership.com> Date: Tue, 22 Mar 2011 08:35:04 -0500
> The API will round up so that the correct region covers the API. > However, if you have other structures packed into the space (as very > often happens on stack), you get cache line interference in the CPU if > they get accessed: The act of accessing an adjacent object pulls in > cache above your object and destroys DMA coherence. This is the > principle reason why DMA to stack is a bad idea.
Another major real reason we can't DMA on-stack stuff is because the stack is mapped virtually on some platforms.
And that is the original reason the restriction was put in place.
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