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xen-devel
Re: [Xen-devel] early_cpu_init() and identify_cpu()
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To: |
"Jan Beulich" <jbeulich@xxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] early_cpu_init() and identify_cpu() |
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From: |
Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> |
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Date: |
Mon, 16 Jul 2007 10:23:29 +0100 |
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Cc: |
xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir@xxxxxxxxxxxxx> |
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Mon, 16 Jul 2007 02:14:31 -0700 |
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> significant (though I assume WC would at best help a little, I'm considering
> other approaches, too): Scrolling a 1280x1024x16 screen takes, on the test
> system I'm primarily trying this out on, on the order of a second. This is
A lot of work on this has been done in X by the X and Gnome developers
including producing some routines which use the largest possible aligned
loads to reduce the big cost (which is PCI reads). Having a write
combining video memory can help (but some cards also put stuff like
command queues there which X cannot WC).
It is usually much cheaper to simply rewrite a text display onto a
framebuffer than scroll it as you can avoid any PCI read traffic so you
get streaming WC writes (or async sse writes even without that). Even
more so when you skip unchanged quadwords.
Alan
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