P2V WinXP guest running verrrry slow. What to do?

[splendid]

I too experience the huge slowness. I did a P2V on a WinXP using vm converter. Did you try to install the virtualbox additions package yet? I am going to try it and see.

[MarkCranness]

@mpack: It sounded dubious to me also, but when Microsoft say: "It is widely understood in the PC industry that for multiprocessor systems, 8259 Programmable Interrupt Controllers (PICs) are insufficient and Advanced Programmable Interrupt Controllers (APICs) are needed", I tend to believe them.

They also say: "Intel has been building local APICs into their processors since the Pentium P54c in 1994. Computers built with genuine Intel processors already contain part of the APIC system. ... However, without an I/O APIC in the system, the local APICs are useless." and "PIC Hardware Can't Do Multiple Processors", so yes some of that is built into a multi-core CPU but it sounds like motherboard support (IO APIC) is needed as well.

More directly at your host setup: You are not using the Multiprocessor version of ntoskrnl.exe (which has 'Original Filename=ntkrnlmp.exe) and Task Manager only shows one CPU... If I were you I would backup and tweak with HALu!

[mpack]

Mark, as a day job I write code for embedded devices, working close to bare metal. I really don't need Microsoft to tell me what an interrupt controller does. With respect, I am not looking for vague press releases and blogs - or even for advice on how to configure my PC. I am instead asking a particular question: what specific extra functionality is provided by a multiprocessor HAL in Windows running on an n-core CPU? In particular, does Windows only use one core otherwise, or is multi-core more a feature of the CPU than the OS? I ask because on my Core 2 Duo PC with a uniprocessor HAL it "feels" like both cores are being used - for example the UI remains fully responsive even when I deliberately run a process that takes up 99-100% CPU. It isn't so long since I used a single core CPU, so I expect the operations in the shell in that situation (starting another task, dragging a window) to get slow and jerky.

In fact I just tried kicking off two instances of that process. Task manager never showed the sum of their CPU times to be greater than 100%, however they both seemed to be running at a decent lick and again the shell remained responsive. Puzzled.

On the other hand I may indeed try switching to a multiprocessor HAL as you suggest (edit: in fact I just did, I made an Acronis backup first, but everything went smoothly - task manager now shows two CPU panes, and that process now caps out at 50%).

[splendid]

I got it fixed. It was the Anti-Virus program that is slowing down everything. Remember AV programs put a hook to the windows kernel, which MS is not recommending doing it so for ages.

[MarkCranness]

I am ... asking a particular question: what specific extra functionality is provided by a multiprocessor HAL in Windows running on an n-core CPU? In particular, does Windows only use one core otherwise, or is multi-core more a feature of the CPU than the OS?

I think it is almost certain that Windows only uses a single core, unless a multiprocessor HAL is used.
Linux (and probably other OSs) can use a multiprocessor/multicore CPU without IO APIC, but Windows can't.
Multi-core is always a feature of the OS, in that unless the OS supports it, only the first core will ever be used.