From owner-freebsd-questions Thu Jun 17 13:16:47 1999 Delivered-To: freebsd-questions@freebsd.org Received: from cygnus.rush.net (cygnus.rush.net [209.45.245.133]) by hub.freebsd.org (Postfix) with ESMTP id 7C13D15548 for ; Thu, 17 Jun 1999 13:16:40 -0700 (PDT) (envelope-from bright@rush.net) Received: from localhost (bright@localhost) by cygnus.rush.net (8.9.3/8.9.3) with SMTP id QAA13807; Thu, 17 Jun 1999 16:16:47 -0400 (EDT) Date: Thu, 17 Jun 1999 15:16:46 -0500 (EST) From: Alfred Perlstein To: mike@hyperreal.org Cc: questions@freebsd.org Subject: Re: Optimizing IDE performance revisited In-Reply-To: <19990617172206.21155.qmail@hyperreal.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Thu, 17 Jun 1999 mike@hyperreal.org wrote: > Alfred Perlstein wrote: > > Enabling PIO or DMA doesn't do all that much for transfer rate, however > > it offloads a lot of work from the CPU. > > > > Before I enabled DMA on my boxes, during heavy compiles top showed > > about 50% or more CPU devoted to "interupt" (processing hardware IO) > > when i switched to DMA it went to under 1% :) > > > > PIO probably isn't as drastic, but can probably spare you mucho cycles. > > I've already enabled PIO mode 3 in the BIOS, and there are no options to enable > any kind of DMA (this is a 1994ish on-board PCI IDE controller). > > Is there something else that I need to configure in the kernel to enable PIO > or DMA? yes, set your IDE flags to 0xa0ffa0ff , or some subset of that, check the LINT kernel config file, some machines that don't support DMA will hang if DMA is enabled, so double check it. > > if you want to see raw read performance try this: > > dd if=/dev/rwd0 of=/dev/null bs=512 count=1000 > > How do I interpret the results? simply, just compare the before and after, before you enabled PIO/dma and after you enabled it, you should see a gain in transfer speed, or a decrease in CPU utilization (you can monitor it via the "top" command) unless there is a specific reason not to, please "cc" all questions to the list it orginiated on, we don't want to deprive people of what we re learning do we? :) -Alfred To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message