From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1Iibck-0006j4-IT for user-mode-linux-devel@lists.sourceforge.net; Thu, 18 Oct 2007 13:05:42 -0700 Received: from saraswathi.solana.com ([198.99.130.12]) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1Iibch-0005we-FC for user-mode-linux-devel@lists.sourceforge.net; Thu, 18 Oct 2007 13:05:42 -0700 Date: Thu, 18 Oct 2007 16:04:32 -0400 From: Jeff Dike Message-ID: <20071018200432.GA9204@c2.user-mode-linux.org> References: <1f154f440710161936h4800b0c5nb3140ff504212625@mail.gmail.com> <20071017155504.GD9497@c2.user-mode-linux.org> <1f154f440710170916j4fdb857fw40c9b2fd2b66f63f@mail.gmail.com> <20071017171920.GA10388@c2.user-mode-linux.org> <1f154f440710171243x40898f8bq386c91c59789fb42@mail.gmail.com> <20071017204527.GB12812@c2.user-mode-linux.org> <1f154f440710171629meb5a3ces92b8fdeacc371857@mail.gmail.com> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: <1f154f440710171629meb5a3ces92b8fdeacc371857@mail.gmail.com> Subject: Re: [uml-devel] Dramatic drop in C3 state residency with NO_HZ patches List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Hrishikesh Cc: user-mode-linux-devel@lists.sourceforge.net On Wed, Oct 17, 2007 at 07:29:47PM -0400, Hrishikesh wrote: > No, I think I haven't been clear enough. The story is right :-) When it is > "busy-looping" like in the second case is when the C3 residency comes down, > as expected. Like you said, it looks broken, and has to be fixed. Yes, your original post was a bit confusing: > This happens when you run a > patched kernel but without the NO_HZ and HR timers options disabled. To my highly logical mind, that double-negative says that you saw the C3 drop with NO_HZ and hrtimers enabled. There was also this, which I paid insufficient attention to: > This does not happen when the tickless option _is_ enabled. However, it does look like the tickless support induces UML into a busy loop when NO_HZ is disabled. BTW, can you measure C3 time with a before-NO_HZ UML, so we can see that NO_HZ has some sort of benefit on power consumption? Jeff -- Work email - jdike at linux dot intel dot com ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel