Date: Mon, 16 Feb 1998 04:37:24 -0800 From: Mike Smith <mike@smith.net.au> To: Brian McGovern <bmcgover@cisco.com> Cc: hackers@FreeBSD.ORG Subject: Re: Mapping phyical memory in to the PCI address range... Message-ID: <199802161237.EAA06311@dingo.cdrom.com> In-Reply-To: Your message of "Thu, 12 Feb 1998 23:28:39 EST." <199802130428.XAA10774@bmcgover-pc.cisco.com>
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Sorry for the delay in following up here. > >> The question at hand was whether it was 'faster' to have the board transfer > >> the data to the HOST's memory, so that a bcopy or b_to_q() call would > >> be moving data from HOST memory to HOST memory, or is the gain insufficient, > >> and its more prudent to have the HOST CPU move the data from the board > >> itself. > > > >It will definitely be faster to have the board push to host memory. > > > Any idea on roughly "how much faster"? I realize this is dependant on a lot of > things, but I'd hate to spend the time doing it if its going to have a minimal > impact. It depends entirely on lots of things. 8) Without actually watching timing diagrams of the device on the bus, and considering how much of the driver's time is actually spent servicing I/O requests, it's impossible to give any sort of real estimate. > Which brings me back to my initial issue. Whats the best way to allocate > RAM in the kernel (I'm assuming a malloc call), and then lock the memory down, > and determine the PCI address, so I can give it to the card to use? If you can do it at boot time, use contigmalloc() and then kvtop() to get the base address of the region. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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