From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arthur Kepner Subject: Re: [PATCH] use mmiowb in tg3_poll Date: Mon, 30 May 2005 09:30:13 -0700 (PDT) Message-ID: References: <200410211628.06906.jbarnes@engr.sgi.com> <20050528231209.GA8456@xi.wantstofly.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: netdev@oss.sgi.com, jesse.barnes@intel.com, gnb@sgi.com Return-path: To: Lennert Buytenhek In-Reply-To: <20050528231209.GA8456@xi.wantstofly.org> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Sun, 29 May 2005, Lennert Buytenhek wrote: > ..... > I'm quite curious what kind of MMIO read latency you see on your > Altix boxen. This app is quite useful for determining those figures > on x86{,_64} machines: > > http://svn.gnumonks.org/trunk/mmio_test/mmio_test.c > .... [cc list change: jbarnes@engr.sgi.com -> jesse.barnes@intel.com] Haven't tried this program yet (though it looks interesting.) In the past I've instrumented the driver with get_cycles() to acquire the PIO read and mmiowb() latencies. I quickly looked through the records that I have and, unfortunately, wasn't able to locate raw data. But I found some scrawlings in my notes which say the most recent measurements for an Altix are: i) PIO read latency ~ 2.4 usec ii) mmiowb() latency ~ 1.1 usec (This data was taken when the PIOs/mmiowb()s were coming from a CPU which was "nearest" to the NIC.) If you have data for x86{,_64}, I'd be interested in that, too. -- Arthur