Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946036Ab2K2Aaf (ORCPT ); Wed, 28 Nov 2012 19:30:35 -0500 Received: from mga14.intel.com ([143.182.124.37]:1310 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945979Ab2K2Aae convert rfc822-to-8bit (ORCPT ); Wed, 28 Nov 2012 19:30:34 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,180,1355126400"; d="scan'208";a="223980605" From: "Liu, Chuansheng" To: Don Zickus CC: "akpm@linux-foundation.org" , "mingo@kernel.org" , "rjw@sisk.pl" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH V2] watchdog: optimizing the hrtimer interval for power saving Thread-Topic: [PATCH V2] watchdog: optimizing the hrtimer interval for power saving Thread-Index: AQHNzX7b3jIJ+7OOuEWyXb6VsTJe75f/9QTQ Date: Thu, 29 Nov 2012 00:30:30 +0000 Message-ID: <27240C0AC20F114CBF8149A2696CBE4A1DD2BA@SHSMSX101.ccr.corp.intel.com> References: <1353602906.15558.1695.camel@cliu38-desktop-build> <1354101892.15558.1699.camel@cliu38-desktop-build> <20121128154242.GS14805@redhat.com> In-Reply-To: <20121128154242.GS14805@redhat.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] 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: 1296 Lines: 28 > It seems like a better approach would be to adjust the timer somehow when > you change c-states. The whole point of the hard and softlockup is to > detect if scheduled code is either deadlock or hogging the cpu for too long. > > If the cpu is in a deep sleep, then nothing is running, right? Which > means nothing can deadlock or hog the cpu. In those cases you can > probably temporarily disable the lockup detector until the cpu wakes up > from that c-state and starts scheduling code again. > You are right, I ever tried the thought, when CPU is idle, we can pause the hrtimer, After wakeup, we resume the hrtimer again. But I found sometimes the in idle and out of idle is too frequent. Anyway, you advice seems the right way, I will try to dig something more deeply. Thanks. > In that case you can really maximize your power savings (and probably get > powerTop to stop telling everyone to disable the nmi_watchdog :-) ). > > Ideally in a deep sleep you don't want any soft interrupts running, no? > > Just a thought. > > Cheers, > Don -- 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/