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Date: Thu, 13 Mar 2008 00:24:10 +0100 From: Stefan Richter <stefanr@...6.in-berlin.de> To: David Moore <dcm@....EDU> CC: Jarod Wilson <jwilson@...hat.com>, linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org Subject: Re: [PATCH] firewire: fw-ohci: sync AT dma buffer before use David Moore wrote: > 1. The dma_sync should probably be done before the context_append > because the controller could in theory start reading the data as soon as > context_append is called right? Yes, but its syncing is superfluous anyway, as mentioned in the other post. *If* it is doing something for Jarod's setup, then only because of side effects like memory barrier properties. > 2. As an optimization, we should attempt to allocate the payload in the > lower 32-bits of physical memory, to prevent extra memcopies on x86_64. > I think this can be done by adding GFP_DMA32 to kmalloc where the > payload was allocated in fw-cdev.c. There might be other places where > we would benefit from GFP_DMA32 also. Of course, these optimizations > are probably better saved for another patch. I think so too. GFP_DMA32 would be appropriate on machines with "software IOMMU" alias swiotlb. Does GFP_DMA32 have adverse affects on machines with a real IOMMU? -- Stefan Richter -=====-==--- --== -==-- http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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