Re: kvm very slow

[Ulrich Schreiner <ulrich.schreiner-sZDnKEZIvs8b1SvskN2V4Q@public.gmane.org>]

today morning i compiled kvm-33 and the output of kvm-stat is much
better now (guest in idle):

kvm statistics

 efer_reload  10944273    6504
 exits        13722688    6967
 halt_exits    1084344     935
 invlpg              0       0
 io_exits      7668914    5070
 irq_exits       27886       2
 irq_window      11477       1
 light_exits   2778416     462
 mmio_exits    2153709     498
 pf_fixed      1085923       0
 pf_guest       459144       0
 request_irq         0       0
 signal_exit     25818       0
 tlb_flush      228295       5


i don't know if these numbers are ok; do you still need the generated
qemu.log for ioport access? if you need it i will upload it to my public
server.

but: the system is slow. it is extremely slow when booting and the
guest-system clock ist twice as slow as the host-system clock (both are
idle; ok, the host as a runnung qemu-instance :-).

when starting i get:

Could not configure '/dev/rtc' to have a 1024 Hz timer. This is not a
fatal
error, but for better emulation accuracy either use a 2.6 host Linux
kernel or
type 'echo 1024 > /proc/sys/dev/rtc/max-user-freq' as root.

well i HAVE a 2.6kernel (2.6.22.1-41.fc7), but i cannot set
dev.rtc.max-user-freq, i only can set the high precision event timer

dev.hpet.max-user-freq = 1024

which i have done. but the message always appears. i don't know if this
is ignorable.







Am Dienstag, den 07.08.2007, 00:44 -0700 schrieb Dor Laor:
> >no ideas what can be done? why it is so slow?
> 
> Let's try to catch the cause for the 74k ioexits per second.
> Please add #define DEBUG_IOPORT in qemu/vl.c and qemu/exec.c and
> recompile.
> After that when the guest runs and does 74k ioexits on idle, enter the
> qemu's monitor (ctrl-alt-1)
> enter 'log ioport'. All guest's ioport access will be written to
> /tmp/qemu.log.
> Be kind enough to calculate the statistics of ioport access per port
> number a second.
> With the numbers we can see the hardware that causes the slowness.
> -- Dor.
> 
> btw: are you using kvm-33 or older?
> 
> >
> >i've tried the "-L /usr/shar/kvm" to use the kvm-bios but no better
> >performance ...
> >
> >Am Donnerstag, den 02.08.2007, 11:24 +0300 schrieb Avi Kivity:
> >> Ulrich Schreiner wrote:
> >> > dmesg|grep kvm
> >> >
> >> > SELinux: initialized (dev kvmfs, type kvmfs), uses genfs_contexts
> >> > kvm: emulating exchange as write
> >> >
> >> >
> >>
> >> There may be messages that aren't prefixed with 'kvm:' (that's a bug
> >> btw).  Please check.
> >>
> >> > now booting into a F7 image, after the system is ready (and in
> >idle):
> >> >
> >> > top
> >> >    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+
> >COMMAND
> >> > 14917 root      20   0  332m  71m  66m S    6  0.9   1:17.05 qemu-
> >kvm
> >> > 14954 root      20   0 14552 1072  812 R    0  0.0   0:00.01 top
> >> >      1 root      20   0 10320  680  572 S    0  0.0   0:02.02 init
> >> >
> >> > kvm_stat (snapshot):
> >> >
> >> > kvm statistics
> >> >
> >> >   exits        12254399   79079
> >> >   halt_exits     326543    4632
> >> >   invlpg              0       0
> >> >   io_exits      6539798   74320
> >> >   irq_exits       43523      29
> >> >   irq_window       4984       0
> >> >   mmio_exits    1319016       0
> >> >   pf_fixed      3140955      56
> >> >   pf_guest       448187       6
> >> >   request_irq         0       0
> >> >   signal_exit     39728       0
> >> >   tlb_flush       29511      31
> >> >
> >>
> >> Wow -- lots of I/O exits.  What does 'top' in the guest say? 'hdparm
> >> /dev/hda' in the guest?
> >>
> >> > when logging into the virtual machine (via ssh) the virtual world
> is
> >> > very slow: i set the time with "ntpdate" and wait exact one minute
> >in
> >> > reality. in the virtual image only 24sec are gone!
> >> >
> >> > and everything else in the image is really slow.
> >> >
> >> >
> >>
> >
> >
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