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The_Document
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Joined: 03 Feb 2018
Posts: 275
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 Posted: Sat Feb 24, 2018 7:05 am Post subject: QEMU is very slow |
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| I have installed QEMU with Aqemu and after experiencing its horrible slowness I thought I would try virtualbox. To my surprise virtualbox is way faster, note I have kernel setup properly with kv-amd loaded along with virtualization options enabled in kernel. WHAT can possibly be causing qemu to be so slow, VB is even faster in graphics performance than QEMU and QEMU is supposed to be faster than VB so there is without a doubt a misconfiguration here. What should I do to correct this? |
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mike155
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Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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| Posted: Sat Feb 24, 2018 8:53 am Post subject: |
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| Did you forget option '-enable-kvm'? |
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 1:45 pm Post subject: |
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| mike155 wrote: | | Did you forget option '-enable-kvm'? |
For which package? |
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szatox
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Joined: 27 Aug 2013
Posts: 3135
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| Posted: Sat Feb 24, 2018 1:51 pm Post subject: |
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Not for a package. For invocation, when you're tarting qemu.
How you start it? What is the full command line? What emulated hardware you use? |
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 1:59 pm Post subject: |
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| szatox wrote: | Not for a package. For invocation, when you're tarting qemu.
How you start it? What is the full command line? What emulated hardware you use? |
-enable-kvm wasen't included and also graphics options don't seem to be optimal here either (I don't know what is optimal) this is what aqemu uses:
| Code: | /usr/bin/qemu-system-x86_64 \
-monitor stdio \
-soundhw hda \
-machine accel=kvm \
-m 1024 \
-cdrom /home/zakhar/Documents/windows-install.iso \
-hda /home/zakhar/.aqemu/Windows_7_x64_HDA.img \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" |
I tried:
| Code: | /usr/bin/qemu-system-x86_64 \
-monitor stdio \
-soundhw hda \
-machine accel=kvm \
-m 1024 \
-cdrom /home/zakhar/Documents/windows-install.iso \
-hda /home/zakhar/.aqemu/Windows_7_x64_HDA.img \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64"
-enable-kvm <----------------- |
here is lsmod to prove kvm-amd is loaded:
https://paste.pound-python.org/show/5ZSOQumzdVcEZs1IRFlJ/
but still SLOOW how to correct this? |
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szatox
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Joined: 27 Aug 2013
Posts: 3135
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| Posted: Sat Feb 24, 2018 7:00 pm Post subject: |
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Well, at this point you should have full performance your CPU offers (though some instruction sets won't be available inside your VM -> you have to enable them explicitly).
Also, you seem to run it with SDL graphic, which indeed is not the best one performance-wise. Consider switching graphics from default cirrus to qxl and replacing SDL console with SPICE.
Bonus point, not related to cpu or graphic performance, but still a thing you may want to improve: virtio does much better job than emulated IDE pulled in by the ancient syntax of "-hda <device image>" |
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frostschutz
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Joined: 22 Feb 2005
Posts: 2977
Location: Germany
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mike155
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Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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| Posted: Sat Feb 24, 2018 7:22 pm Post subject: |
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1) Is it just a typo? Or did you forget a backslash at the end of the line before '-enable-kvm'?
| Code: | [...]
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" <-- missing backslash?
-enable-kvm
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2) You should check in the QEMU Monitor that kvm is enabled: what is the output of 'info kvm'?
3) What exactly do you mean by 'slow'? Windows itself? A program you start? Disk I/O? Graphics? |
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 8:05 pm Post subject: |
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| mike155 wrote: | 1) Is it just a typo? Or did you forget a backslash at the end of the line before '-enable-kvm'?
| Code: | [...]
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" <-- missing backslash?
-enable-kvm
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2) You should check in the QEMU Monitor that kvm is enabled: what is the output of 'info kvm'?
3) What exactly do you mean by 'slow'? Windows itself? A program you start? Disk I/O? Graphics? |
The issue with slowness would be booting from windows 10 installation iso, virtualbox starts installation process waaaayy sooner than qemu, also virtual box boots windows wayyy faster than qemu does.
Out put from qemu montior after running info kvm:
| Code: |
kvm support: enabled
(qemu) |
Here is new qemu command line:
| Code: | /usr/bin/qemu-system-x86_64 \
-monitor stdio \
-smp 1,threads=1 \
-soundhw hda \
-vga qxl \
-machine accel=kvm \
-m 1024 \
-cdrom /home/zakhar/Documents/windows-install.iso \
-drive file="/home/zakhar/.aqemu/Windows_7_x64_HDA.img",if=virtio \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" \
-enable-kvm |
Very slow and weird I don't know how to fix this issue, qemu is nicer to use since it scales the screen more nativly than VB does. I sincerely believe this is an issue with appropriate cpu flags not being issued. What should I do about the slowness issue qemu has? |
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mike155
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Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 8:36 pm Post subject: |
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It was of no help I tried this:
| Code: | /usr/bin/qemu-system-x86_64 \
-monitor stdio \
-soundhw hda \
-vga qxl \
-machine accel=kvm,kvm_shadow_mem=1843200 \
-m 1024 \
-no-fd-bootchk \
-cdrom /home/zakhar/Documents/windows-install.iso \
-drive file="/home/zakhar/.aqemu/Windows_7_x64_HDA.img",if=virtio \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" \
-enable-kvm \
-cpu host |
and this
| Code: |
/usr/bin/qemu-system-x86_64 \
-monitor stdio \
-soundhw hda \
-vga qxl \
-machine accel=kvm,kvm_shadow_mem=1843200 \
-m 1024 \
-no-fd-bootchk \
-cdrom /home/zakhar/Documents/windows-install.iso \
-drive file="/home/zakhar/.aqemu/Windows_7_x64_HDA.img",if=virtio \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" \
-enable-kvm \
-cpu host,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time \
-machine type=pc |
Still too slow to use. |
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szatox
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Joined: 27 Aug 2013
Posts: 3135
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| Posted: Sat Feb 24, 2018 8:41 pm Post subject: |
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I've just noticed you're trying to run windows there, on a VM with barely 1GB RAM.
Are you sure your VB doesn't work faster simply by using more resources?
Hell, does windows even booth with 1GB RAM those days? |
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 8:47 pm Post subject: |
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| szatox wrote: | I've just noticed you're trying to run windows there, on a VM with barely 1GB RAM.
Are you sure your VB doesn't work faster simply by using more resources?
Hell, does windows even booth with 1GB RAM those days? |
Gave VM 3GBs RAM was of no help. This issue is leading me to belive I need wine, but it shouldn't be unresolvable there should be something incorrect about this. Here are use flags for qemu:
https://paste.pound-python.org/show/md0bsm97FecuGFvbFbqL/ |
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mike155
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Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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| Posted: Sat Feb 24, 2018 9:09 pm Post subject: |
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6) What happens if you remove parameter ',kvm_shadow_mem=1843200'? I've never seen that parameter before. I don't think it's wrong - but just to be sure...
7) Your image files are in your home directory. There's nothing wrong with that. But: is this a hard disk or a ssd? On my computer, /home is a NFS mount and that would give terrible results...
8 ) What does 'top' on you host system show when you start QEMU? 100% CPU load all the time? |
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The_Document
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Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 11:09 pm Post subject: |
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| mike155 wrote: | 6) What happens if you remove parameter ',kvm_shadow_mem=1843200'? I've never seen that parameter before. I don't think it's wrong - but just to be sure...
7) Your image files are in your home directory. There's nothing wrong with that. But: is this a hard disk or a ssd? On my computer, /home is a NFS mount and that would give terrible results...
8 ) What does 'top' on you host system show when you start QEMU? 100% CPU load all the time? |
6. I tried without kvm_shadow many times, still slow
7. Im on an SSD
8. Most of the time not 1 core is utilized to its max, but not with VB, many cores are used beyong 75% with VB and it starts installing windows much faster than with qemu. |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54236
Location: 56N 3W
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| Posted: Sat Feb 24, 2018 11:19 pm Post subject: |
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The_Document,
says to allocate a singe core anh single thread to the guest.
Is that the way you run VBox too?
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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mike155
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Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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| Posted: Sat Feb 24, 2018 11:19 pm Post subject: |
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| Quote: | | but not with VB, many cores are used beyong 75% with VB |
... so what about QEMU parameters '-smp 2' or even '-smp 4' ? |
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The_Document
Apprentice
Joined: 03 Feb 2018
Posts: 275
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| Posted: Sat Feb 24, 2018 11:36 pm Post subject: |
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| NeddySeagoon wrote: | The_Document,
says to allocate a singe core anh single thread to the guest.
Is that the way you run VBox too? |
No I didn't need to configure ANYTHING cpu wise with VB. Then I learned VB has processor settings too and VB is way faster than qemu on 1 core, so I increased the guest cores to 4 and it was EVEN FASTER. I ran qemu with:
| Code: | /usr/bin/qemu-system-x86_64 \
-monitor stdio \
-soundhw hda \
-vga qxl \
-machine accel=kvm,kvm_shadow_mem=1843200 \
-m 3072 \
-no-fd-bootchk \
-cdrom /home/zakhar/Documents/windows-install.iso \
-drive file="/home/zakhar/.aqemu/Windows_7_x64_HDA.img",if=virtio \
-boot once=d,menu=off \
-net none \
-rtc base=localtime \
-name "Windows 7 x64" \
-enable-kvm \
-cpu host \
-smp 4,threads=1 |
But qemu is still way too slow. Because my AMD cpu has no support for hyperthreading which is an Intel product, it can only support 1 thread per core . Really its real name is SMT but raising threads above 1 gives:
| Code: | | (qemu) qemu-system-x86_64: AMD CPU doesn't support hyperthreading. Please configure -smp options properly. |
so I leave it 1 thread per core as it normally should be, at any rate its still SLOW and did not speed up. I would be VERY happy with VB but its main gripe would be its resolution scaling, which is abominable when compared to qemu, I should mention qemu has excellent screen scaling and if its full screen its virtually impossible to distinguish whether the OS is on a VM or not. Qemu is still very slooow. |
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