From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4B7DC3A4.7000503@domain.hid> Date: Thu, 18 Feb 2010 14:48:04 -0800 From: Thomas Lockhart MIME-Version: 1.0 References: <0C632A1C-3B64-462B-9892-380CB14F6AD8@domain.hid> <4B7DC07C.5@domain.hid> In-Reply-To: <4B7DC07C.5@domain.hid> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] Analogy DIO speed List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexis Berlemont Cc: Peter Pastor Sampedro , "xenomai@xenomai.org" > It is not that bad, no ? Does anybody have an accurate idea on the > duration of a common ioctl on such a powerful machine ? Yikes! My limited and possibly out of date understanding of the PCI bus would say that you risk a much larger latency and jitter in just getting access to the bus. I'd be happy with anything in the 1us range (1-5?) which afaicr is what it takes to negotiate the bus and to write one or a few longwords to a device. This is without something already on the bus doing DMA or some other block transfer which could push up the latency much higher since a block transfer is not required to give up the bus for some larger amount of time (please excuse my possible mangled use of terms which may have other specific meaning in the PCI spec). If folks expect much better performance (perhaps from modern revs of PCI??) I'd like to hear of their experience... - Tom