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Anatomy of Linux Kernel Shared Memory

Posted by kdawson on from the culture-by-another-name dept.

An anonymous reader sends in an IBM DeveloperWorks backgrounder on Kernel Shared Memory in the 2.6.32 Linux kernel. KSM allows the hypervisor to increase the number of concurrent virtual machines by consolidating identical memory pages. The article covers the ideas behind KSM (such as storage de-duplication), its implementation, and how you manage it.

2 of 93 comments (clear)

  1. Re:First Post by Abcd1234 · · Score: 5, Insightful

    If your OS isn't sharing duplicate memory blocks already, you're using a shitty OS. (Linux already shares dup read only blocks for many things, like most modern OSes).

    Umm, no.

    Most modern OSes share memory for executable images and shared libraries. In addition, some OSes, such as Linux, support copy-on-write semantics for memory pages in child processes created with fork (note, Solaris is an example of an OS that *doesn't* do this).

    Aside from that, there is no automated sharing of memory between processes. Frankly, I have no idea where you got the idea there was.

  2. Re:First Post by Abcd1234 · · Score: 4, Insightful

    Aside from all the places that memory is shared between processes, theres no sharing between processes ... yea, I totally get you ...

    That's exactly right. I pointed out all the places. *All of them*. And there's *two*: shared, read-only executable pages, and the heaps of children created by COW-enabled forks. That's it. That's all.

    So any new technology for memory de-duping is impressive because, traditionally, it just ain't done. Which directly contradicts the content of your original post.

    Perhaps now you understand?