On 07/27/2013 07:41 PM, Marco Stornelli wrote:
Il 26/07/2013 14:29, Vladimir Davydov ha scritto:
Hi,
We want to propose a way to upgrade a kernel on a machine without
restarting all the user-space services. This is to be done with CRIU
project, but we need help from the kernel to preserve some data in
memory while doing kexec.
The key point of our implementation is leaving process memory in-place
during reboot. This should eliminate most io operations the services
would produce during initialization. To achieve this, we have
implemented a pseudo file system that preserves its content during
kexec. We propose saving CRIU dump files to this file system, kexec'ing
and then restoring the processes in the newly booted kernel.
http://pramfs.sourceforge.net/
AFAIU it's a bit different thing: PRAMFS as well as pstore, which has
already been merged, requires hardware support for over-reboot
persistency, so called non-volatile RAM, i.e. RAM which is not directly
accessible and so is not used by the kernel. On the contrary, what we'd
like to have is preserving usual RAM on kexec. It is possible, because
RAM is not reset during kexec. This would allow leaving applications
working set as well as filesystem caches in place, speeding the reboot
process as a whole and reducing the downtime significantly.
Thanks.
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