Query regarding physically discontiguous memory
From: Valdis.Kletnieks at vt.edu <hidden>
Date: 2013-12-25 15:37:35
On Wed, 25 Dec 2013 14:45:01 +0530, Pritam Bankar said:
This is what I don't understand what does it mean by containing large holes? physical discontiguous memory? Is it like when I put 2 RAM chips in a system then memory for them will be discontiguous?
Per my understanding RAM memory will ALWAYS be contiguous whether its 512 MB or 4 GB.
Your understanding is wrong. That may be true on most x86-based desktops and laptops and the like, but it's often very wrong on other architectures. In fact, given that the x86 architecture is just one of like 27 archs that Linux supports, it's a good bet that there's more archs that *don't* enforce contiguous memory than do. Counting through the defconfigs to get a number is left as an exercise for the student. :) A common case for embedded systems is "256M of RAM at address 0, and 256M of RAM at address 0x80000000" (or whatever the halfway mark for the architecture is). NUMA boxes are sometimes "each node's RAM is at <node number>*4G" or similar, which means lots of holes if each node is partly populated with only 2G. -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 848 bytes Desc: not available Url : http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20131225/086ee853/attachment.bin