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Takehara 12-24-09 05:54 AM

shared memory pixmaps
Would you tell me how to use shared memory pixmaps of MIT-Shared Memory Extension?

My graphic card is
Product Name: Quadro FX 5800
Driver Version: 185.18.36

and, we set the option "AllowSHMPixmaps" to "1" in "xorg.conf".

We checked it by the function:XShmQueryVersion whether X Window System can use shared memory pixmaps or not. As a result, the pixmaps argument returned false. It means the system cannot use shared memory pixmaps, so I want to know how to utilize the shared memory pixmaps.

Sincerely yours

Thunderbird 12-24-09 07:15 AM

Re: shared memory pixmaps
Check the Xorg log file if the drivers recognized the line you added. So how did you add it? The right way would be to add the line: Option "AllowSHMPixmaps" "1" to the right screen or device section.

Do you really need shared memory pixmaps? It is and old feature and should not be used in modern apps as you won't receive much hardware acceleration. If possible use another mechanism. If your app uses OpenGL use pixel buffer objects (PBOs) which offer roughly similar functionality.

Linuxhippy 12-24-09 09:01 AM

Re: shared memory pixmaps
Shared memory pixmaps can be considered legacy and should be avoided if possible.
EXA/UXA based drivers don't support it anymore at all.

Use shared memory images instead and ShmPut/GetImage this should give you the same features,but is supported on all major platforums.

- Clemens

Takehara 01-04-10 06:52 AM

Re: shared memory pixmaps
Thank you for your advices.

We can use shared memory pixmaps by increasing the size of shared memory.
The size can be changed to 256MB by the following command;

# echo 268435456 > /proc/sys/kernel/shmmax

After that, the pixmaps argument of XShmQueryVersion function becomes true, so it means that we can use shared memory pixmaps.

The default size of shared memory is 32MB, and we have set the screen resolution 3840x2400. I thought that The default size might not be enough to the resolution.

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