RB W wrote:
[snip]
The video can also be a performance killer. The Intel solution uses
shared memory, which means memory access has to be divided up between
the graphics and the CPU which leads to contention. You don't specify if
the AMD solution with the Radeon X1270 has dedicated memory or not. If
you have dedicated memory for the video, you are going to get better
performance because you won't have memory contention.
I was thinking that if under XEN everything is networked I could run
only one instance using the actual video and then either SSH to the
CentOS and other instances and/or VNC/ssh forward the GUI apps as
needed. Do I still run into contention in this scenario? In effect I
was thinking of running every instance "headless" except for the one I
want to "See". I would be comfortable with this because Linux is
getting to the point where "pagers" have so many variations you can
segregate anything into any number of virtual presentations of local
and remote apps.
[snip]
The competition between video and the CPU for RAM still exists with a
shared memory arrangement. The video has to refresh the screen at a
certain rate, usually 60 times a second. For each pixel on the screen
you are probably reading out 3 bytes for 24 bit color. RAM timing for
video is a hard limit, so the CPU has to yield for every video access,
so the CPU suffers. Of course, you might have so much excess processing
power for what you are doing that you will never notice.
Gus
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