From: Bob Booth - UIUC (booth@UIUC.EDU)
Date: Thu Nov 21 2002 - 09:44:29 EST
I guess I'll stick my neck out...
Backing store used to be a problem on older X servers, and systems short on
memory. The X server used to take up a significant amount of memory (still
does in my opinion), and think still to this day is plagued by memory leaks.
Turning on backing store and save unders will speed things up for screen
repaints, and desktop switches, since various portions of the Xservers
memory and frame buffer are stored in a ramcache. On newer systems, with the
newer servers with lots of memory to spare, it shouldn't be a problem to
turn it on anymore, however, watch your Xserver memory with top, nmon or
ps. Depending on the window manager you use, X will really take off, and if
my machine is any indication, will never come back (unless you restart X).
I'm not sure how IBM's implementation of openGL deals with the X server and
WM, but I think it moves most of the bulky part of the server out of the way.
In short, I don't think turning it on is going to hurt you, unless you are
short on memory. Saveunders are insignificant. Watch your X server memory,
and keep it under control, that might be half your problem with the crashes.
bob
On Thu, Nov 21, 2002 at 08:27:09AM -0500, cbaker@GOODYEAR.COM wrote:
> Does no one have any BackingStore experience? Maybe my question is too
> simple or too long? Any bit of wisdom would be greatly appreciated.
>
> We have an inhouse software development team that has written a number of
> graphical analysis programs. They were originally written for users on Sun
> and HP workstations, but have also been ported to AIX (4.3.3).
>
> My problem is that the programs get all screwed up and finally crash on the
> RS/6000, unless I turn on Backing Store by adding the X extension "-BS" in
> "/usr/lpp/X11/defaults/xserverrc".
>
> I have always been told that you will greatly impact the speed of the
> RS/6000 graphics on the console if you turn on Backing Store or
> Save-Unders. Now they want me to turn on BS and wouldn't mind also having
> Save_Unders if possible.
>
> I say this is just poor programming on their part. We have plenty of
> programmers of OpenGL on our RS/6000 and they never needed to rely on the X
> server to handle their screen refreshes.
>
> So, my question is: Am I wrong about the effects this -BS X extension will
> have on the normal daily graphical activities done on these RS/6000's ?
>
> Christopher M. Baker
> Senior Technical Support Analyst
> DSE/TCO
> Goodyear Tire and Rubber Company
>
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