From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: Interrupt Latency 2.6.33.7 rt30 Date: Fri, 26 Aug 2011 09:48:36 +0200 Message-ID: <20110826074836.GO16557@pengutronix.de> References: <4E56B8A5.6080306@gmx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users To: Christian Kraus Return-path: Received: from metis.ext.pengutronix.de ([92.198.50.35]:33768 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781Ab1HZHsh (ORCPT ); Fri, 26 Aug 2011 03:48:37 -0400 Content-Disposition: inline In-Reply-To: <4E56B8A5.6080306@gmx.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Thu, Aug 25, 2011 at 11:03:33PM +0200, Christian Kraus wrote: > Hello > I have wrote a GPIO-driver, that toggle the value of a GPIO when a > interrupt is comming from an another GPIO. > When I measure the latency between the interrupt and the toggled Pin > it's about ten times higher than without the rt-patch. > (without Patch =3D 8-11 us > with Patch =3D 30-110 us) It's expected and known that an rt kernel has a worse average latency. Having said that I cannot say if the increase you see is "too much". The best option you have is asking ftrace what happens in these 30-110 us after making sure you have a decent sched_clock implementation. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= | -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html