From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Subject: Re: Using patch-2.6.33.7.2-rt30 increases latency and CPU usage? Date: Fri, 11 May 2012 13:56:22 +0000 (UTC) Message-ID: References: <4FAAEBF3.10907@netacquire.com> <20120510135320.GA9568@grante> To: linux-rt-users@vger.kernel.org Return-path: Received: from plane.gmane.org ([80.91.229.3]:41978 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753475Ab2EKN4i (ORCPT ); Fri, 11 May 2012 09:56:38 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1SSqKh-0007Y7-D9 for linux-rt-users@vger.kernel.org; Fri, 11 May 2012 15:56:35 +0200 Received: from dsl.comtrol.com ([64.122.56.22]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 11 May 2012 15:56:35 +0200 Received: from grant.b.edwards by dsl.comtrol.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 11 May 2012 15:56:35 +0200 Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 2012-05-11, Remy Bohmer wrote: > Hi, > > 2012/5/10 Grant Edwards : >>> If the 20usec requirement is hard, you can also look at using an FIQ. >> >> Does the normal AT91 kernel not use FIQs at all? ?If so, I might be >> able to dedicate the FIQ to this function and have it happen without >> the Linux kernel knowing about it (or affecting it). ?Any >> communication between it and a normal user-task would have to be >> handled carefully... > > No, the kernel does not use the FIQ at all. It is free for you to use > as you want. Communication with the FIQ handler can be done using a > queue based on atomic instructions. Thanks! I was about to start looking into that... -- Grant Edwards grant.b.edwards Yow! I just forgot my whole at philosophy of life!!! gmail.com