From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: Info: NAPI performance at "low" loads Date: 19 Sep 2002 09:03:39 -0600 Sender: netdev-bounce@oss.sgi.com Message-ID: References: <1032381789.20498.151.camel@irongate.swansea.linux.org.uk> <20020918.134630.127509858.davem@redhat.com> <1032383727.20463.155.camel@irongate.swansea.linux.org.uk> <20020918.142250.130847722.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: alan@lxorguk.ukuu.org.uk, ebiederm@xmission.com, hadi@cyberus.ca, akpm@digeo.com, manfred@colorfullife.com, netdev@oss.sgi.com, linux-kernel@vger.kernel.org Return-path: To: "David S. Miller" In-Reply-To: <20020918.142250.130847722.davem@redhat.com> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org "David S. Miller" writes: > From: Alan Cox > Date: 18 Sep 2002 22:15:27 +0100 > > It doesnt matter what XFree86 is doing. Thats just to load the PCI bus > and jam it up to prove the point. It'll change your inb timing > > Understood. Maybe a more accurate wording would be "a fixed minimum > timing". Why? If I do an inb to a PCI-X device running at 133Mhz it should come back much faster than an inb from my serial port on the ISA port. What is the reason for the fixed minimum timing? Alan asserted there is a posting behavior difference, but that should not affect reads. What is different between mmio and pio to a pci device when doing reads that should make mmio faster? Eric