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Re: [Qemu-devel] Re: Extremely slow graphic updates

From: Lennart Sorensen
Subject: Re: [Qemu-devel] Re: Extremely slow graphic updates
Date: Wed, 21 Jan 2009 16:29:21 -0500
User-agent: Mutt/1.5.13 (2006-08-11)

On Wed, Jan 21, 2009 at 08:06:38PM +0000, Stefano Stabellini wrote:
> I am afraid your patch shouldn't make a difference because sdl doesn't
> have a dpy_copy function so with sdl dpy_update is always called.
> Besides none calls qemu_console_copy but graphic cards so passing
> '-serial /dev/null -parallel /dev/null' shouldn't change anything in
> this regard.
> In any case I tried passing '-serial /dev/null -parallel /dev/null' as
> arguments but (locally) I do not see any benefits (I tested with the
> debian ppc installation cd).
> Could you please tell me if you see the slowdown on a local X server also?
> The sdl blitting functions are optimized to be run locally, it is
> possible that they do not have good performances on a remote X server.
> Fortunately we provide a much better interface to connect to qemu
> remotely (vnc), that now should be even faster than before.

No it is not slow locally.

Now can you explain why my patch made it no longer slow remotely because
it did fix the problem for me.  can you explain why changing -serial and
-parallel to /dev/null made it not slow?

So without my patch it runs fine locally.  It runs slow remotely.

With my patch it runs fine locally and remotely.

Without my patch but using -serial /dev/null -parallel /dev/null it runs
fine locally and remotely.

Something more than just a dpy_update must be happening in dpy_copy.
Looking at the code I don't quite see what it could be doing, unless
there is a long list of listeners initiallized some of which do have a
copy function.

So either my patch does something, or I have got my builds mixed up and
have some other patch in now that fixes it.  Maybe I will go do a fresh
checkout and build and test that then just to be sure.

Len Sorensen

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