New linux kernels

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I like reading kernel chagelogs. There is usually at least one NEAT thing in there. This time (2.6.32) that's a memory de-duplication technology that will be of great benefit for VM environments.
The result is a dramatic decrease in memory usage in virtualization environments. In a virtualization server, Red Hat found that thanks to KSM, KVM can run as many as 52 Windows XP VMs with 1 GB of RAM each on a server with just 16 GB of RAM. Because KSM works transparently to userspace apps, it can be adopted very easily, and provides huge memory savings for free to current production systems. It was originally developed for use with KVM, but it can be also used with any other virtualization system - or even in non virtualization workloads, for example applications that for some reason have several processes using lots of memory that could be shared.
So. Cool. And there is more:
To make easier a local configuration, a new build target has been added - make localmodconfig. It runs "lsmod" to find all the modules loaded on the current running system. It will read all the Makefiles to map which CONFIG enables a module. It will read the Kconfig files to find the dependencies and selects that may be needed to support a CONFIG. Finally, it reads the .config file and removes any module "=m" that is not needed to enable the currently loaded modules. With this tool, you can strip a distro .config of all the unuseful drivers that are not needed in our machine, and it will take much less time to build the kernel. There's an additional "make localyesconfig" target, in case you don't want to use modules and/or initrds.
If you want to build a monolithic kernel for some reason, they've just made that a LOT easier. I made one a long while back in the 2.4 era and it took many tries to be sure I got the right drivers compiled in. Turn off module support and you've just made a kernel that's harder to rootkit. I don't see this improvement being as widely useful as the previous, but it is still nifty.

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