[Qemu-devel] qemu (cvs-version) performance?

[Qemu-devel] qemu (cvs-version) performance?

[Sven Köhler]

Hi,

i'd like to know, what the qemu-project aims at.
Do the authers aim at writing (together with kqemu or qv86) an
alternative to VMWare? (At least in the x86 virtualization case)

I first thought that way and i still hope that, but i was disappointed
by qemu 0.8.0 and the latest version from CVS.

I thought, that qemu-0.8.0's problem would be disk-IO. I installed
Windows 2000 and in the task-manager the CPU-Time is 100% during intense
IO. A "dir c:\ /A /S /B >NUL:" on the console causes 100% CPU-time and
most of it being that red-colored "in-kernel-time".

The DMA-mode is active according to the device-manager, since i upgraded
to qemu CVS (version from an hour ago).

So IO still seems to be very expensive. AFAIK, IDE-DMA or BusMastering
should enable the CPU to do other things while waiting for the Interrupt
that signals the finished transfer. (My knowledge about hardware is not
that good though.) But the virtual CPU is not idle and the host's CPU
isn't either.

Of course i'm using kqemu.


So what might be wrong?
Some hints:
- the disk-image(raw format) is on a reiserfs-filesystem
- the host ist kernel 2.6.15


Please don't understand me wrong.
I appreciate your work.


Greetings
  Sven

[Qemu-devel] qemu (cvs-version) performance?

[Sven Köhler]

Hi,

i'd like to know, what the qemu-project aims at.
Do the authers aim at writing (together with kqemu or qv86) an
alternative to VMWare? (At least in the x86 virtualization case)

I first thought that way and i still hope that, but i was disappointed
by qemu 0.8.0 and the latest version from CVS.

I thought, that qemu-0.8.0's problem would be disk-IO. I installed
Windows 2000 and in the task-manager the CPU-Time is 100% during intense
IO. A "dir c:\ /A /S /B >NUL:" on the console causes 100% CPU-time and
most of it being that red-colored "in-kernel-time".

The DMA-mode is active according to the device-manager, since i upgraded
to qemu CVS (version from an hour ago).

So IO still seems to be very expensive. AFAIK, IDE-DMA or BusMastering
should enable the CPU to do other things while waiting for the Interrupt
that signals the finished transfer. (My knowledge about hardware is not
that good though.) But the virtual CPU is not idle and the host's CPU
isn't either.

Of course i'm using kqemu.


So what might be wrong?
Some hints:
- the disk-image(raw format) is on a reiserfs-filesystem
- the host ist kernel 2.6.15


Please don't understand me wrong.
I appreciate your work.


Greetings
  Sven

Re: [Qemu-devel] qemu (cvs-version) performance?

[Paul Brook]

> I thought, that qemu-0.8.0's problem would be disk-IO. I installed
> Windows 2000 and in the task-manager the CPU-Time is 100% during intense
> IO. A "dir c:\ /A /S /B >NUL:" on the console causes 100% CPU-time and
> most of it being that red-colored "in-kernel-time".

Qemu host IO is syncrhonous. ie. the guest is paused on the instruction that 
issues the IO until the IO completes. As for as the guest is concerned it 
happens instantly. This is all your test shows.

Paul