[PC-BSD Dev] Wild idea to speed up boot process

Claudio L. claudio at hpgcc3.org
Sat Aug 10 09:12:08 PDT 2013


On 08/10/2013 05:21, Luca Ferrari wrote:
> Uhm...sounds to me like a duplicate of the vnode cache layer: each 
> time access to a file is detected you have to map it to the ramdisk, 
> and then the system maps it into the vnode cache. 
Not exactly, because the cache is empty on boot, and you have to 
populate it as you access the files, triggering a lot of random reads, 
on files that will likely be used only once during boot.
Traditional caches are not very efficient during boot, unless they are 
persistent, like the L2ARC.


> I don't know if this will produce a real gain considering the 
> complexity it adds. Something that could work better, in my opinion, 
> is an autonomous system able to "adjust" a ramdisk each time the 
> system powers off so that the next time it boots the ramdisk would be 
> still valid considering any changes the user has done in the system 
> itself (e.g., configuration files). Luca

That was exactly what I was proposing: this ram disk has to be 
persistent, otherwise there's no improvement at all.

Claudio



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