From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5265A173.4030608@xenomai.org> Date: Mon, 21 Oct 2013 23:49:39 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Slow Sockets and Pipes with POSIX Skin List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Neil T. Dantam" Cc: xenomai@xenomai.org On 10/21/2013 11:41 PM, Neil T. Dantam wrote: > I am seeing some surprisingly high latencies for socket and pipe > communication using Xenomai's POSIX skin. Pipes, localhost TCP/UDP, > and local domain sockets all show worst case latency of ~100us on > Xenomai 2.6.2.1/Linux 3.4.6 on a Xeon E3-1270v2. Average and 99% > latency is under 20us. Running `xeno-test latency` gives worst-case > latency of ~10us. POSIX message queues have worst case latency below > 20us. > > I've done the following to reduce latency: > > * Disabled CPU frequency scaling > * Disabled USB > * Set real-time scheduling priority > * Prefaulted the stack > > The 100us delay seems like what one get from a System Management > Interrupt (SMI). However, since `xeno-test latency` and message > queues both show low latency, it seems unlikely that this could be the > issue. > > Has anyone else encountered (or not encountered) similar performance > issues with pipes and sockets? Xenomai posix skin does not handle pipes, and only handles TCP/IP sockets if you have installed and configured rtnet. -- Gilles.