Re: [Qemu-devel] [PATCH] A simple way to DMA (and async. IO) to make win2003 happy

[Fabrice Bellard <fabrice@bellard.org>]

Juergen Pfennig wrote:
> Hello ...
> 
> Please note: I will send the Async IO stuff later, see below.
> 
> This Patch: Here is a very simple patch to ide.c that does not change
>             the controller type and that lets an existing win2003 in-
>             stallation use multi-sector IO and/or DMA.
 > [...]

I just merged a more complete patch from Jens Axboe. Does it give 
acceptable performance in win2003 ?

> (3) My way to async IO is different, read below. The implementation
>     does async read and write. My plans are to make the SDL async too.
> 
> (4) The async IO layer integrates well with Fabrice Bellard's IOHandlers.
>     In fact vl.c needs no modifications, the code uses a pipe to signal
>     that IO got ready. The modifications on the block driver layer are
>     minimal.
> 
> To say this again: the async IO stuff itself is about 600 lines of code
> (in one file) but it needs several small changes in qemu. Here are some
> fake definitions that you might help you to get a first impression:

So there are two async I/O patches now :-)

I am more interested by these patches now because I want to improve the 
performance to match (or exceed !) the performance of the other 
virtualizers. I have at least 5 items on my TODO list :

1) New kqemu which virtualizes both user and kernel code (currently in 
alpha stage but not released yet).

2) DMA block I/O (merged)

3) async block I/O (not merged yet)

4) Network adapter using DMA (not merged yet)

5) VGA acceleration (either improve Cirrus VGA or switch back to Bochs 
VGA for Win 2000/XP or Linux)

Fabrice.