Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422837AbWHYEzb (ORCPT ); Fri, 25 Aug 2006 00:55:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161004AbWHYEzb (ORCPT ); Fri, 25 Aug 2006 00:55:31 -0400 Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:60257 "HELO smtp102.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1161003AbWHYEza (ORCPT ); Fri, 25 Aug 2006 00:55:30 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=D5cvi0dBQGSrlM+04dtr5ckt3pBfrKCcjy8Z9I43swR97Xo9YsuQdjVQxOKYqqthwRbVFdLgenhLxYEsm0RjRHHAj0FS6ADNCMFdHTmKUmK8WEe/BKNw01c5Alg0d1lqD71wh0kPtrbSUL8MO/IcvrPZPLRNQ0s3aNs0DbcTTa4= ; Message-ID: <44EE829C.10606@yahoo.com.au> Date: Fri, 25 Aug 2006 14:54:52 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Arjan van de Ven CC: Jesse Barnes , linux-kernel@vger.kernel.org, len.brown@intel.com, Arjan van de Ven Subject: Re: [RFC] maximum latency tracking infrastructure References: <1156441295.3014.75.camel@laptopd505.fenrus.org> <200608241408.03853.jbarnes@virtuousgeek.org> <44EE1801.3060805@linux.intel.com> In-Reply-To: <44EE1801.3060805@linux.intel.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1385 Lines: 35 Arjan van de Ven wrote: > Jesse Barnes wrote: > >> On Thursday, August 24, 2006 10:41 am, Arjan van de Ven wrote: >> >>> The reason for adding this infrastructure is that power management in >>> the idle loop needs to make a tradeoff between latency and power >>> savings (deeper power save modes have a longer latency to running code >>> again). >> >> >> What if a processor was already in a sleep state when a call to >> set_acceptable_latency() latency occurs? > > > there's nothing sane that can be done in that case; any wake up already > will cause the unwanted latency! > A premature wakeup is only making it happen *now*, but now is as > inconvenient a time as any... > (in fact it may be a worst case time scenario, say, an audio interrupt...) Surely you would call set_acceptable_latency() *before* running such operation that requires the given latency? And that set_acceptable_latency would block the caller until all CPUs are set to wake within this latency. That would be the API semantics I would expect, anyway. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/