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: 18 Sep 2002 11:27:34 -0600 Sender: netdev-bounce@oss.sgi.com Message-ID: References: <3D87A59C.410FFE3E@digeo.com> <20020917.180014.07882539.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: 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: <20020917.180014.07882539.davem@redhat.com> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org "David S. Miller" writes: > From: jamal > Date: Tue, 17 Sep 2002 20:57:58 -0400 (EDT) > > I am not so sure with that 6% difference there is no other bug lurking > there; 6% seems too large for an extra two PCI transactions per packet. > > {in,out}{b,w,l}() operations have a fixed timing, therefore his > results doesn't sound that far off. ???? I don't see why they should be. If it is a pci device the cost should the same as a pci memory I/O. The bus packets are the same. So things like increasing the pci bus speed should make it take less time. Plus I have played with calibrating the TSC with outb to port 0x80 and there was enough variation that it was unuseable. On some newer systems it would take twice as long as on some older ones. Eric