Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753088AbZJUXq1 (ORCPT ); Wed, 21 Oct 2009 19:46:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752118AbZJUXq1 (ORCPT ); Wed, 21 Oct 2009 19:46:27 -0400 Received: from smtp-outbound-1.vmware.com ([65.115.85.69]:43010 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752013AbZJUXq0 convert rfc822-to-8bit (ORCPT ); Wed, 21 Oct 2009 19:46:26 -0400 From: Bela Lubkin To: "'Corey Minyard'" , Randy Dunlap CC: "discuss@LessWatts.org" , "Kok, Auke" , Arjan van de Ven , "openipmi-developer@lists.sourceforge.net" , lkml Date: Wed, 21 Oct 2009 16:46:41 -0700 Subject: RE: [Openipmi-developer] [Discuss] [PATCH] ipmi: use round_jiffies on timers to reduce timer overhead/wakeups Thread-Topic: [Openipmi-developer] [Discuss] [PATCH] ipmi: use round_jiffies on timers to reduce timer overhead/wakeups Thread-Index: AcpSjEuExcQJDzppT7Knairll6LBYwAGu4Jg Message-ID: References: <20091021102822.5b32b2dc.randy.dunlap@oracle.com> <20091021114210.4d7e1ea9@linux.intel.com> <4ADF57D7.7010808@intel.com> <20091021130348.cd521b0c.randy.dunlap@oracle.com> <4ADF6D76.7070409@acm.org> In-Reply-To: <4ADF6D76.7070409@acm.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1711 Lines: 37 Corey Minyard & Randy Dunlap wrote: Randy>> From what I recall (probably 2 years ago), [older] ipmi hardware Randy>> does not generate event interrupts, so it has to be polled. Randy>> Randy>> Corey, can you elaborate on this? Corey> Certainly. Yes, some (probably most) IPMI hardware does not use Corey> interrupts, and unfortunately, it's not just older machines. Corey> The driver used to poll more slowly, but in many cases the Corey> performance was unacceptable. Corey> Corey> kipmid is only started if the hardware doesn't support Corey> interrupts, so only users with sub-standard hardware have to Corey> suffer with this problem. Regrettably, of the "big three" in the "PC Server" world, only HP's iLO2 BMC supports interrupts. Dell's DRAC4 & 5 don't, IBM's ASM, RSA, etc. don't. Also (at least out of a sample of one) SuperMicro also doesn't have an interrupt. They also have all settled on the KCS interface, which dribbles one character through per non-interrupt. So sad. Dell's DRAC3 had a BT BMC which transferred whole IPMI packets via DMA _and_ had an interrupt. HP's ancient SMIC equipment also had an interrupt (but that's also char-by-char, and their current KCS has an interrupt, so at least they haven't regressed). I've guessed that some chip vendor must have come out with a Really Cheep KCS implementation and drove every other implementation out of the market. :-( I've heard rumors that some current Sun hardware has BT. >Bela<-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/