From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55968) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YH8wS-0008D1-IP for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:36:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YH8wP-00066s-Ca for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:36:48 -0500 Received: from greensocs.com ([193.104.36.180]:3452) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YH8wO-00066F-UE for qemu-devel@nongnu.org; Fri, 30 Jan 2015 05:36:45 -0500 Message-ID: <54CB5EB5.7050902@greensocs.com> Date: Fri, 30 Jan 2015 11:36:37 +0100 From: Frederic Konrad MIME-Version: 1.0 References: <20150129203728.6cb9271e@crunchbang> <54CABD0A.1090207@redhat.com> <54CB34CB.20805@siemens.com> <20150130112644.3ab44d84@crunchbang> In-Reply-To: <20150130112644.3ab44d84@crunchbang> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] QEMU and Real Time OS List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?B?TWFyYyBNYXLDrQ==?= , Jan Kiszka Cc: Paolo Bonzini , Marcelo Tosatti , qemu-devel , Luiz Capitulino On 30/01/2015 11:26, Marc Mar=C3=AD wrote: > El Fri, 30 Jan 2015 08:37:47 +0100 > Jan Kiszka escribi=C3=B3: >> On 2015-01-30 00:06, Paolo Bonzini wrote: >>> >>> On 29/01/2015 20:37, Marc Mar=C3=AD wrote: >>>> Is this an expected behaviour? I can't see why. >>>> >>>> I'd like to know if there is a certain reason why it doesn't work. >>>> Or if it should work and the problem is too much I/O overhead. Or >>>> any other hint to understand it. >>> It is due to latencies in the host. You need at least to use >>> preempt-rt kernels in the host as well. >> That alone won't help much. You also need to fine-tune the guest to >> avoid running into QEMU locks that continuously synchronizes the guest >> on things like VGA or disk I/O emulation. >> >> When using KVM, thus being able to run VCPUs widely independent of >> each other and the device models, you need to push cyclictest on an >> isolated second virtual CPU of the guest. Luiz and Marcelo can >> probably confirm this based on their ongoing experiments. >> >> With TCG, we would first of all have to make it true SMP and >> independent of the I/O device lock. That's what Frederic is working >> on [1]. >> >> Jan >> >> [1] http://permalink.gmane.org/gmane.comp.emulators.qemu/314406 >> > Thanks for the answers. I think I'm stuck with ARM926, which I think is > not prepared for SMP. I'll have to look if I can use Cortex for my > experiments. > > I'll continue interested with the improvements for RT on TCG, but for > the moment I'll go to work on real harware, even though is easier to > run and debug on an emulator. > > Thanks > Marc Hi Marc, I think the important point here is "TCG thread independent of the I/O=20 device lock". I need it for multithread TCG but that doesn't mean you need an SMP guest platform for that. Fred