From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: on the wire behaviour of TSO on/off is supposed to be the same yes? Date: Fri, 21 Jan 2005 12:18:53 -0800 Message-ID: <41F163AD.5070400@hp.com> References: <41F1516D.5010101@hp.com> <200501211358.53783.jdmason@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: netdev@oss.sgi.com In-Reply-To: <200501211358.53783.jdmason@us.ibm.com> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org Jon Mason wrote: > The benefit of TSO is not throughput, but CPU utilization. Throughput > increase is usually a side effect because of better PCI DMA behavior (eg. > large PCI transfers are better). I'm not looking for a throughput increase, the systems involved are already capable of link-rate without TSO, just looking for throughput to not drop with TSO. If it were a throughput drop because the NIC CPU (bletch) saturated that would be one thing (such as happened with Tigon2 in another context) but this drop stems from what appears to be not filling cwnd and getting acks delayed by a timer. > Are you seeing a CPU utilization decrease? Yes, at the cost of occasional pauses in the data stream. TSO is on TCP STREAM TEST to 192.168.13.1 Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 131072 262142 262142 10.00 843.86 12.77 -1.00 2.480 -1.000 TSO is off TCP STREAM TEST to 192.168.13.1 Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 131072 262142 262142 10.00 941.13 22.82 -1.00 3.972 -1.000 This is with tcp_tso_win_divisor set to 1 so TSO kicks-in before 200some-oddK are transfered. The service demand drop (modulo the accuracy of CPU util measurements via the -DUSE_PROC_STAT stuff) is rather nice. rick jones subscribed, so mail to netdev will reach me - no need for separate cc