From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sujit K M Subject: Re: mq_timedrecieve timeout accuracy Date: Wed, 24 Mar 2010 18:51:25 +0530 Message-ID: <921ca19c1003240621k226df80ct62b3fb2e26269eca@mail.gmail.com> References: <6d09081c1003240527r471ee34etbba11b4b7c7e92b3@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users@vger.kernel.org, rachana.rao@in.abb.com To: Pradyumna Sampath Return-path: Received: from mail-pw0-f46.google.com ([209.85.160.46]:47338 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756210Ab0CXNV0 convert rfc822-to-8bit (ORCPT ); Wed, 24 Mar 2010 09:21:26 -0400 Received: by pwi5 with SMTP id 5so3897512pwi.19 for ; Wed, 24 Mar 2010 06:21:25 -0700 (PDT) In-Reply-To: <6d09081c1003240527r471ee34etbba11b4b7c7e92b3@mail.gmail.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: > stumbled upon the fact that the timeout in the mq_timedrecieve is > innaccurate to the tune of a more than 5-6 miliseconds and that it is > fairly consistent even at its highest priority. OK. > > Cyclictest on the same machine gives me a max deviation of about 7uS, > so I guess my timers (hrt) are functioning alright. Out of how much? What is the range of the timer. > Here is a small program I hacked up from the LTP sources to > demonstrate this behaviour (attached). I ran this on a dual core > 2.5Ghz cpu and a uniprocessor 1.5Ghz cpu (cpuinfo below). On the > dual-core I can see that its off by 1-2 miliseconds but on the 1.5 Gh= z > celeron its off by 6-8 miliseconds sometimes. Yes, but the cyclic test doesnot match with this result. Both are in the negative. How have you tested the patch. > > kernel version: 2.6.33.1-rt10 > > Usage: ./send_rev_2 > > $ cat /proc/cpuinfo > processor =A0 =A0 =A0 : 0 > vendor_id =A0 =A0 =A0 : GenuineIntel > cpu family =A0 =A0 =A0: 6 > model =A0 =A0 =A0 =A0 =A0 : 13 > model name =A0 =A0 =A0: Intel(R) Celeron(R) M processor =A0 =A0 =A0 =A0= 1.50GHz > stepping =A0 =A0 =A0 =A0: 8 > cpu MHz =A0 =A0 =A0 =A0 : 1500.111 > cache size =A0 =A0 =A0: 1024 KB > fdiv_bug =A0 =A0 =A0 =A0: no > hlt_bug =A0 =A0 =A0 =A0 : no > f00f_bug =A0 =A0 =A0 =A0: no > coma_bug =A0 =A0 =A0 =A0: no > fpu =A0 =A0 =A0 =A0 =A0 =A0 : yes > fpu_exception =A0 : yes > cpuid level =A0 =A0 : 2 > wp =A0 =A0 =A0 =A0 =A0 =A0 =A0: yes > flags =A0 =A0 =A0 =A0 =A0 : fpu vme de pse tsc msr pae mce cx8 apic s= ep mtrr pge mca cmov > clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx up bts > > Also attaached is my .config. > > thanks in advance > regards > /prady > > > -- > http://www.prady.in > --=20 -- Sujit K M blog(http://kmsujit.blogspot.com/) -- 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