Re: [Qemu-devel] More about slow clock in guest OS

["Mulyadi Santosa" <mulyadi.santosa@gmail.com>]

hello Sergey...

On 1/31/08, Sergey Bychkov <sergb@unichrom.com> wrote:
> As I can see, this document anything about what to do if qemu hung :)

reading always helps in some degree :)

> After some investigations I can say that with the latest (2008/01/30) qemu
> from cvs, compiled with gcc-3.4 on linux x86_64 host, guest OS win2k3 works
> not too good.
So, in other words "it works but not so well". may I interpret it as a progress?

> With "-clock dynticks" clock in OS is very slow - and windows time server
> can't adjust.

Probably due to cost of Qemu timer rearming. And maybe Windows 2003
does certain dyntick by its own...thus enlarging the timer rearming
cost.

> With "-clock rtc" hung periodically - for up to 5 minutes, 300 seconds.

pffff... too much timers get expired? lock contention somewhere...anybody?

>This
> could happen at bootstrap - when no OS, only BIOS. Then it resumes and works
> for some random period of time, then hangs again, and so on. This behaviour
> doesn't depend on guest OS, and was reproduced with Knoppix live CD. Note
> that host should be periodically busy executing something like torrent
> client.
Thus..maybe it's Qemu's fault...

> Details and startup scripts:
>
> $ cat knoppix-qemu-nographic.sh
> ==
> QEMU=$HOME/bin/qemu-system-x86_64
> [ -x "$QEMU" ] || QEMU=/usr/bin/qemu-system-x86_64
> sudo modprobe kqemu
> echo will use executable $QEMU
> DIR=`dirname $0`
> [ -z "$DIR" -o "$DIR" == "." ] && DIR=`pwd`
> echo DIR is $DIR
> PREV_RTC_FREQ=`cat /proc/sys/dev/rtc/max-user-freq`
> [ "$PREV_RTC_FREQ" -ge "1024" ] || echo 'WARN: RTC FREQ too slow:'
> $PREV_RTC_FREQ
> sudo $QEMU -net nic,model=rtl8139,macaddr=52:54:00:80:80:01 -net
> tap,script=$DIR/qemu-ifup-br0,downscript=$DIR/qemu-ifdown-br0 -localtime -cdrom
> /distrib/knoppix/KNOPPIX_V5.1.0CD-2006-12-30-EN.iso -m 384 -pidfile
> $DIR/virt1-knoppix.pid -smp 1 -no-kqemu -clock rtc -vnc :9

Ehm:
1. can you simply use SDL output instead of VNC?
2. what if you don't use -localtime? just courious...

> ==
> $ cat /proc/sys/dev/rtc/max-user-freq
> ==
> 4096
> ==

ehm...I think 1024 is enough for most cases..

> $ uname -a
> ==
> Linux *** 2.6.18-5-amd64 #1 SMP Sat Dec 22 20:43:59 UTC 2007 x86_64
> GNU/Linux
> ==

is that kernel version of the host? can you upgrade it ? let's say to
the latest 2.6.24?

PS: could you try KVM too? but ehm...well, sounds like you don't have
VT enabled Intel processor or SVM enabled AMD processor. So, if you
indeed have one...try KVM..

regards,

Mulyadi.