User`s guide

Tuning the SGI Media Server (Setting the Maximum DMA Size)

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vtr.main.timing_standard 625

Note: The system timing standard controls the default video output timing only if the

control vtr.media.video.output.timing is not changed from its default value of

system. The vtr.media.video.output.timing control appears in the

/usr/vtr/config/system-defaults/MFCODEC_n ﬁles.

Tuning the SGI Media Server (Setting the Maximum DMA Size)

The maximum direct memory access (DMA) size limits the maximum amount of data

that can be transferred to or from the ﬁlesystem in a single operation. The default

maximum DMA size is 4 MB, which is too small for most installations. To increase the

system’s maximum DMA size, use the following procedure:

1. As superuser, start systune to change the DMA size:

# systune -i

Updates will be made to running system and /unix.install

systune->

2. Enter the new DMA size:

systune-> maxdmasz bytes

The following example shows a speciﬁcation of 641 pages, which translates to

approximately 10 MB (641 * 16K):

systune-> maxdmasz 641

maxdmasz = 257 (0x101)

Do you really want to change maxdmasz to 640? (y/n)

3. Enter y for yes.

The system responds as follows:

In order for the change in parameter maxdmasz to become effective,

reboot the system

4. Quit systune:

systune-> quit

5. Reboot the server: