Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!tuvie!vmars!alex From: alex@vmars.tuwien.ac.at (Alexander Vrchoticky) Newsgroups: comp.arch Subject: Re: Incremental sync()s and using disk idle time Message-ID: <2380@tuvie.UUCP> Date: 14 Mar 91 13:46:41 GMT References: <10773@dog.ee.lbl.gov> <3236@crdos1.crd.ge.COM> <1991Mar12.194704.17859@zoo.toronto.edu> <1991Mar13.195708.28678@zoo.toronto.edu> Sender: news@tuvie.UUCP Lines: 22 henry@zoo.toronto.edu (Henry Spencer) writes: >it can actually hurt performance. (As a case in point, the DMA on the >LANCE Ethernet chip ties up your memory far longer than data transfers >by a modern CPU would.) Sigh ... who do you tell? We have been conducting some measurements of the DMA overhead of a single-board computer used for real-time applications. Almost 50 percent of the memory cycles get burned by the LANCE. The aim of the measurements was to see whether we could guarantee that a reasonable and, above all, predictable, amount of CPU power was available for application tasks. In the end we concluded that we'd have to design a dual-processor board with one CPU being dedicated to I/O handling. Which we did. [BTW, I can't see any connection to NFS here, therefore I removed that newsgroup from the Newsgroups-line.] -- Alexander Vrchoticky | alex@vmars.tuwien.ac.at TU Vienna, CS/Real-Time Systems | +43/222/58801-8168 "those who feel they're touched by madness, sit down next to me" (james)