Missing memory

From LinodeWiki

When using the latest kernels (e.g. 2.6.39-x86_64-linode18) you may find that nearly 100MB of your server's memory is "missing". For example on a 512MB Linode, only 425MB is reported:

# free -m
             total       used       free     shared    buffers     cached
Mem:           425        403         21          0         79        137

The full 512 is still there, but a large chunk has been reserved for use by the kernel, and is not available for your apps.

This can be avoided by using a different standard kernel (e.g. 2.6.38-x86_64-linode17), or compiling your own with different .config. If compiling, note that Linode kernels newer than 2.6.35 are not downloadable from Linode Src. Instead Linode build theirs from the vanilla sources from kernel.org.

[edit] Extra info

• -linode kernels contain a lot of unneeded drivers (most notably filesystems like JFS and XFS which aren't default in Linode's current setup (which uses ext3, unless you did some fancy partitioning)