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Re: [Qemu-devel] [PATCH] A simple way to DMA (and async. IO) to make win
Re: [Qemu-devel] [PATCH] A simple way to DMA (and async. IO) to make win2003 happy
Thu, 02 Feb 2006 00:29:21 +0100
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913
Juergen Pfennig wrote:
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
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)