From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from ns1.tyldum.com ([91.189.178.231]:43881 "EHLO ns1.tyldum.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754712Ab1LMSL1 (ORCPT ); Tue, 13 Dec 2011 13:11:27 -0500 Message-ID: <4EE79543.2080802@tyldum.com> Date: Tue, 13 Dec 2011 19:11:15 +0100 From: Vidar Tyldum MIME-Version: 1.0 To: Marko Ristola CC: Linux Media Mailing List Subject: Re: Multiple Mantis devices gives me glitches References: <4EE6FF6F.5050901@kolumbus.fi> In-Reply-To: <4EE6FF6F.5050901@kolumbus.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: 13.12.2011 08:31, Marko Ristola: > > Hi > > Here is a patch that went into Linus GIT this year. > It reduces the number of DMA transfer interrupts into one third. > Linus released 2.6.38.8 doesn't seem to have this patch yet Good news, combining this patch with IRQ management fixes the problem for me. Status: * Stock 2.6.38.8 mantis, no IRQ management: glitches * Stock 2.6.38.8 mantis, with IRQ management: glitches * Patched 2.6.38.8 mantis, no IRQ management: glitches (less) * Patched 2.6.38.8 mantis, with IRQ management: very few glitches * Same as above, but latency_timer set to 0xff: no glitches in one hour The patch was applied to 2.6.38.8 (in Ubuntu terms: 2.6.38-13-generic-pae). Tests involved having VDR record on three different transponders at the same time, which means lots of IO and all three cards active at once. For IRQ management I tried both 'irqbalancer' and manual setting with IRQ affinity (which is basicly what irqbalancer does). I tried playing with the latency timer on the other scenarios, not only the last one, but all had glitches anyways. Not sure what to conclude with: - Unfortunate IRQ handling on this CPU (two and two share IRQ handling)? - Too many interrupts generated by driver (design issues)? - Driver not handling SMP gracefully? ...or a combination? Your patch is definately needed. Is there anything I can do to help getting it in? -- Vidar Tyldum vidar@tyldum.com PGP: 0x3110AA98