Re: [Qemu-devel] objective benchmark?

[Kazu]

Tuesday, May 16, 2006 8:48 PM Lonnie Mendez wrote:

> Kazu wrote:
>
>>If you set /proc/sys/dev/rtc/max-user-freq to 1024 and disable cpuspeed
>>service that is related to SpeedStep/PowerNow! on a host OS, the clock in
>>guest OS works fine.
>>
>>I checked it on i686/x86_64 Linux host.
>>
>   Mind saying how you checked this?  I'm on a pentium-III mobile
> processor and the only way I've seen so far to make qemu + rdtsc behave
> 100% is by disabling ACPI (boot with -noacpi).  If I add a simple printf
> to cpu_calibrate_ticks it doesn't seem fixed to me:
>
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 1126809000
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 17308857
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 103710852
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 15292604
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 96695295
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 1126761234
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 1126762522
> address@hidden /prog/qemu-stuff $ qemu -localtime -hda winxp.img -no-acpi
> -kernel-kqemu -soundhw es1370
> ticks_per_sec set as 49791263
>
>   The first entry is with the patch attached called
> 'ticks_from_proc.patch' applied (I've been using this for almost a
> year).  It sets the value ticks_per_sec, which happens to be used by a
> lot of qemu's hardware emulation, using information in /proc/cpuinfo.
> This doesn't fix the time issue as rdtsc is still used every time a
> SIGALRM signal occurs for timing, but at least the guest's emulated
> hardware runs to speed.
>
> address@hidden /prog/qemu-cvs/qemu-acpi/qemu $ find . -type f -exec fgrep
> -l 'ticks_per_sec' {} \;
> ./audio/audio.c
> ./audio/noaudio.c
> ./audio/wavaudio.c
> ./monitor.c
> ./vl.c
> ./vl.h
> ./hw/acpi.c
> ./hw/adlib.c
> ./hw/arm_timer.c
> ./hw/cuda.c
> ./hw/fdc.c
> ./hw/i8254.c
> ./hw/i8259.c
> ./hw/ide.c
> ./hw/mc146818rtc.c
> ./hw/mips_r4k.c
> ./hw/ppc.c
> ./hw/sb16.c
> ./hw/sh7750.c
> ./hw/slavio_timer.c
> ./hw/usb-uhci.c
>
>   The second patch adds the printf statement so you can see this for
> yourself.
>

Here is values of ticks_per_sec on Athlon 64 3000+ .
i686 host:
1790803394
1790784284
1790774719
1790798849
1790814225

x86_64 host:
1790764763
1790815837
1790816089
1790803590
1790771017

If I changed usleep(50 * 1000) to ulseep(500 * 1000) in vl.c, it improves.

When cpuspeed service is working in x86_64 host, it becomes:
994896127
994896984
994895713
994897215
994896447

It is because CPU is changed from 1.8GHz to 1GHz. TSC is changed dynamically
while QEMU is working.
I think your results are from mobile Pentium III.
I don't know much but a power management of mobile Pentium III works without
software?

I attached a patch that I modifed from your patch. It can be applied by
patch -p0. I checked it works for Athlon 64 with cpuspeed service (Power
Now!). ticks_per_sec changed dynamically but a clock of win2k guest on
x86_64 Linux host works fine.

If your guest OS is Linux, it is necessary to set clock=pit at guest OS'es
startup. TSC may change.

I hope it works for SpeedStep.

I can't test i686 Linux host because ACPI and cpuspeed doesn't work on my
PC.

I think it is better to detect CPU change signal and calibrate
ticks_per_sec.

Regards,
Kazu

qemu-20060517-tps_from_proc.patch
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