From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YzB7L-0001Jl-3T for user-mode-linux-devel@lists.sourceforge.net; Sun, 31 May 2015 21:50:03 +0000 Received: from a.ns.miles-group.at ([95.130.255.143] helo=radon.swed.at) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1YzB7J-0006mT-Q2 for user-mode-linux-devel@lists.sourceforge.net; Sun, 31 May 2015 21:50:03 +0000 Message-ID: <556B8202.6030501@nod.at> Date: Sun, 31 May 2015 23:49:54 +0200 From: Richard Weinberger MIME-Version: 1.0 References: <556AED66.3030706@nod.at> <1433098827.8871.13.camel@m3y3r.de> In-Reply-To: <1433098827.8871.13.camel@m3y3r.de> 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 Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net Subject: Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers To: Thomas Meyer Cc: user-mode-linux-devel Am 31.05.2015 um 21:00 schrieb Thomas Meyer: >> Ping. >> Would be nice to have this patch for the 4.2 merge window. > > I can provide you the current version of the patch, but I'm not sure if > it's ready for inclusion yet. That's fine. I'll look at it. Just rebase it against Linus' tree or uml-next. https://git.kernel.org/cgit/linux/kernel/git/rw/uml.git/log/?h=linux-next > For example: > - With this patch I see new zombie processes of UML userspace > processes. I'm not sure what's going on here. > - Anton reported some hang he sees with this patch > - A person from cicso is worried about the potential idle CPU usage > after the patch, because of the many timers started, i.e. a host with > hundreds of UMLs. > > Also meanwhile I think is not the correct thing to start a new timer > for each UML userspace process, because the timer will also trigger the > userspace process, even the corresponding process isn't scheduled by > the kernel currently. I think the previous behaviour with the itimer > was okay, because the virtual timer only did execute when the process > was executing which is the correct thing to do for the currently active > task in the UML kernel. > I see two solutions for above problem: cascade the kernel timer into > the current active task; there is actually no need to start a timer in > each userspace process. > Start/stop each timer when a userspace process becomes active resp. > becomes inactive again. > I hope above logic makes some sense at all! What do you think about > this? Hm, we definitely don't want a new timer for each userspace proc. The timer has to work as a regular clock source. But I'll have to read your/Anton's code in detail first. Thanks, //richard ------------------------------------------------------------------------------ _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel