From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51618) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VWolk-0000ag-Ga for qemu-devel@nongnu.org; Thu, 17 Oct 2013 10:41:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VWole-00007e-MP for qemu-devel@nongnu.org; Thu, 17 Oct 2013 10:41:44 -0400 Message-ID: <525FF6CE.1010003@ilande.co.uk> Date: Thu, 17 Oct 2013 15:40:14 +0100 From: Mark Cave-Ayland MIME-Version: 1.0 References: <525729E4.6070108@ilande.co.uk> <5257BA59.4010108@redhat.com> In-Reply-To: <5257BA59.4010108@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] PPC: Timer issues with git master List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: "qemu-ppc@nongnu.org" , qemu-devel , alex@alex.org.uk, Alexander Graf On 11/10/13 09:44, Paolo Bonzini wrote: >> I've just upgraded my git repository from around the 1.6 release >> timeframe to git master and I'm seeing some strange timing issues >> running through my OpenBIOS test suite which weren't there before my git >> update. >> >> The two most noticeable changes are in FreeBSD and HelenOS; the >> countdown timer in the FreeBSD bootloader used to count down in seconds >> whereas now it whizzes down to zero, and HelenOS now takes a very very >> long time to boot. >> >> In order to reproduce from git master download the appropriate ISOs and >> launch QEMU like this: >> >> ./qemu-system-ppc -cdrom >> /home/build/src/qemu/image/ppc/FreeBSD-9.1-RC2-powerpc-release.iso -M >> mac99 -m 512 -boot d >> >> ./qemu-system-ppc -cdrom >> /home/build/src/qemu/image/ppc/HelenOS-0.4.2-ppc32.iso -m 512 -boot d >> >> Paulo/Alex B - I know you've been working with timers, so wondered if >> this is related to some of the changes you've been making? I've also >> copied Alex Graf in case this is somehow related to how the timer code >> interacts with the PPC timebase-frequency. > > Can you bisect them? > > Paolo Hi Paolo, I've just attempted a bisection testing HelenOS, but I'm struggling to get a consistent result. Even with the same binary across multiple runs then sometimes I see the issue with frequent timer pauses, and sometimes I don't which makes tracking this down very difficult. What I do see post-timer-rework is that when it does occur, the screen redraws become really really slow; rectangular blocks (maybe 2 per sec or so?) are redrawn very slowly working their way down the screen. I have a feeling from memory that HelenOS does tend to hit the timer interrupts quite hard on PPC so could it be that the new code somehow blocks screen updates under high timer interrupt load? As for the FreeBSD issue, this seems to be something different from the HelenOS issue and I see it even with QEMU 1.6. A quick browse around the git logs points me towards this as a possible suspect: http://git.qemu.org/?p=qemu.git;a=commit;h=a0f9fdfd98cc0571f9921a7eadd7316532e3e289. ATB, Mark.