Problems with performance - Qwt - Xorg with 4 or 6 screens

Giacomo giacomo.strangolino at
Thu Feb 9 07:41:36 PST 2012

Hi to all.

In our organization, Elettra - Synchrotron Radiation Facility, Trieste,
Italy, we have used Qwt since many years now...

After introducing four and six screen computers, working with large
control panel applications with plots displaying data at a refresh rate
of 10Hz has become painful... Two or three of such applications can hang
the whole machine. This is not an issue if the same scenario takes place
in a "traditional" computer with one or at most two screens.

Xorg process is the one that takes 100% of the CPU usage in 4/6 monitor
machines, things getting even worse when the application window (i.e.
the plot inside it) grows in size.

Reading the past messages in the mailing list, there seems to be no way
of using the hardware acceleration to draw Qwt plots.
Nonetheless, we need to find a way to speed up the Xorg drawing process
in order to make our workstations usable even in the case of computers
connected to four or six screens.

In conclusion: is there any hint to optimize Xorg or Qwt paint process
in order to make our applications run smoothly?

In machines with 4 and 6 screens Xorg is slow and takes 100% of CPU also
when other applications require fast repaint of an area, such as a web
page being scrolled...

Thanks for any help 

Hardware configuration:

Intel(R) Core(TM)2 Quad CPU Q9550 @ 2.83GHz


nVidia NVS 450
4 * 20" displays 1600x1200 (DVI-I)
2 * Full HD TVs @ 1920x1080 (DVI-I/HDMI)

Ubuntu 10.04 + KDE 3.5.12 + Qt 4.6.2 + qwt 5.2.0

Thanks, Giacomo.

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