[Ksummit-discuss] [CORE TOPIC] [TECH TOPIC] live kernel patching

Pavel Emelyanov xemul at parallels.com
Tue May 6 13:23:14 UTC 2014


On 05/06/2014 02:08 AM, Jiri Kosina wrote:
> On Mon, 5 May 2014, Andy Lutomirski wrote:
> 
>>> Tons of interest in this topic here, mostly for the in-memory database
>>> workloads.
>>
>> Would in-memory databases be happier if there were a way to kexec
>> without losing your data?
> 
> Well, that's basicaly what criu-based aproach is doing. With the drawback 
> that dumping during checkpointing can take a while for large tasks (such 
> as in-memory databases) I guess.

It does takes a while, but not when there's a lot of memory mapped by tasks.
This is what "preserving memory in place over kexec" is needed for -- we keep
all tasks' memory in memory, thus avoiding long delays due to writing it on
disk into images. Such thing performs poorly when there's a lot of _dirty_
memory hanging around.

Thanks,
Pavel


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