From owner-freebsd-hackers Wed Oct 24 12: 3: 4 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from iguana.aciri.org (iguana.aciri.org [192.150.187.36]) by hub.freebsd.org (Postfix) with ESMTP id CDC5D37B401 for ; Wed, 24 Oct 2001 12:02:59 -0700 (PDT) Received: (from rizzo@localhost) by iguana.aciri.org (8.11.3/8.11.1) id f9OIxde46201; Wed, 24 Oct 2001 11:59:39 -0700 (PDT) (envelope-from rizzo) Date: Wed, 24 Oct 2001 11:59:39 -0700 From: Luigi Rizzo To: hackers@freebsd.org Subject: HW question -- can the CPU timeout on accesses to the PCI bus ? Message-ID: <20011024115939.A46082@iguana.aciri.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.23i Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Well, the question is rather simple... i am running some experiments on system with severe load on the PCI bus (basically a router with 4 interfaces trying to forward 2..4 streams of 64-byte packets at 100Mbit/s (i.e. 144kpps on each stream), and from low level timing i notice that the time to access a status register in the card sometimes goes up in the sky (I have measured well over 10us under heavy load, whereas the normal time is in the order of 0.5-1us). 10us is a fairly long time, and while i can explain it easily (there are 4 active cards in the system, each one with a transmit, receive and control engines trying to access the PCI bus -- and there are two bridges between the CPU and the card), i wonder if the CPU can potentially wait forever to get hold of the bus, or it eventually times out. If so, how can i tell that the operation failed ? cheers luigi ----------------------------------+----------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . ACIRI/ICSI (on leave from Univ. di Pisa) http://www.iet.unipi.it/~luigi/ . 1947 Center St, Berkeley CA 94704 Phone: (510) 666 2927 ----------------------------------+----------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message