Cool ... Simpler is *always* better! We got a code inspection that indicated that memory above 4G would be accessed inefficiently using pci_map_single. Sounds like the IO-Perf howto needs modernization. Sincerely -- Mark Salyzyn > -----Original Message----- > From: James Bottomley [mailto:James.Bottomley@xxxxxxxxxxxx] > Sent: Wednesday, November 30, 2005 1:45 PM > To: Mark Haverkamp > Cc: linux-scsi; Salyzyn, Mark > Subject: Re: [PATCH 3/5] aacraid: update dma mapping > > > On Wed, 2005-11-30 at 10:36 -0800, Mark Haverkamp wrote: > > This patch changes map_single to map_page in compliance with > > recommendations made in the IO-Perf howto document to prevent bounce > > buffering of DMA requests. > > Erm, there's a misunderstanding somewhere. You're replacing correct > pci_map_single calls with its more difficult to use > pci_map_page. This > has absolutely zero performance impact and adds the risk that because > pci_map_page is more complex to use, someone gets it wrong somewhere. > Really, for block devices pci_map_single is the absolutely correct > interface. pci_map_page should really only be used by the > net stack for > packet fragment mapping. > > James > > > - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
