QNX RTOS v4 Knowledge Base
QNX RTOS v4 Knowledge Base
| Title |
The purpose of /dev/shmem |
| Ref. No. |
QNX.000009288 |
| Category(ies) |
Kernel, Filesystem |
| Issue |
What is /dev/shmem? This "device" was found in the filesystem and is taking up an extraordinary amount of hard disk space (~250MB according to some reports). Seeing that the hard disk drive is only 500MB, this becomes a problem. What creates it? What can we expect for it's average size? Can it be deleted ?
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| Solution |
Most devices under /dev are not on the hard drive at all. In particular /dev/shmem is for shared memory. The system creates a large shared memory region which overlays all physical memory. This is usefull for mapping dual ported memory (like VGA). It does not take any physical disk space.
This "device" wasn't found in the filesystem, it was found in the name space. Similar to almost everything else under /dev, this is not on the hard drive, so it isn't taking up any disk space at all. (The fact that the entire filesystem is also a subspace of the name space can make this an easy mistake to make.)
Proc32 creates it. The expected size depends on the version of Proc32, but it will be 4G in the future. No, it can't be deleted - but there is no benefit to being able to delete it. |
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