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Re: IODemoryDescriptor->prepare() Performance relateted to the kIODirection?

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Re: IODemoryDescriptor->prepare() Performance relateted to the kIODirection?

Subject: Re: IODemoryDescriptor->prepare() Performance relateted to the kIODirection?
From: Godfrey van der Linden <email@hidden>
Date: Fri, 9 Feb 2007 14:58:09 +1100

the prepare/complete performance on a memory descriptor are affected by direction. However it makes no difference to your hardware and DMA access is irrelevant.

Specifically IOMemroyDescriptor->prepare() always takes about the same amount of time, but complete on a kIODirectionIn needs to inform the VM system that the pages are now dirty and can't be flushed without paging them out.

Godfrey

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