From mboxrd@z Thu Jan 1 00:00:00 1970 From: lm@bitmover.com (Larry McVoy) Subject: Re: tcp bw in 2.6 Date: Tue, 2 Oct 2007 10:20:02 -0700 Message-ID: <20071002172002.GO17418@bitmover.com> References: <20070929142517.EC6AB5FB21@work.bitmover.com> <20070929172639.GB7037@bitmover.com> <20071002005917.GB5480@bitmover.com> <20071002022059.GE7037@bitmover.com> <47027C63.803@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Larry McVoy , Linus Torvalds , davem@davemloft.net, wscott@bitmover.com, netdev@vger.kernel.org To: Rick Jones Return-path: Received: from ipcop.bitmover.com ([192.132.92.15]:43525 "EHLO mail.bitmover.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754396AbXJBRUD (ORCPT ); Tue, 2 Oct 2007 13:20:03 -0400 Content-Disposition: inline In-Reply-To: <47027C63.803@hp.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Oct 02, 2007 at 10:14:11AM -0700, Rick Jones wrote: > Larry McVoy wrote: > >A short summary is "can someone please post a test program that sources > >and sinks data at the wire speed?" because apparently I'm too old and > >clueless to write such a thing. > > WRT the different speeds in each direction talking with HP-UX, perhaps > there is an interaction between the Linux TCP stack (TSO perhaps) and > HP-UX's ACK avoidance heuristics. If that is the case, tweaking > tcp_deferred_ack_max with ndd on the HP-UX system might yield different > results. I doubt it because I see the same sort of behaviour when I have a group of Linux clients talking to the server. The HP box is in the mix simply because it has a gigabit card and that makes driving the load simpler. But if I do several loads from 100Mbit clients I get the same packet throughput. > WRT the small program making a setsockopt(SO_*BUF) call going slower than > the rsh, does rsh make the setsockopt() call, or does it bend itself to the > will of the linux stack's autotuning? What happens if your small program > does not make setsockopt(SO_*BUF) calls? I haven't tracked down if rsh does that but I've tried doing it with values of default, 64K, 1MB, and 10MB with no difference. > *) depending on the quantity of CPU around, and the type of test one is These are fast CPUs and they are running at 93% idle while running the test. -- --- Larry McVoy lm at bitmover.com http://www.bitkeeper.com