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

Luca Ferrari fluca1978 at infinito.it
Tue Aug 20 23:31:27 PDT 2013


On Wed, Aug 21, 2013 at 2:34 AM, Claudio L. <claudio at hpgcc3.org> wrote:
> On 08/19/2013 19:41, Warner Losh wrote:
>>
>> That's an interesting assertion. But even so, the amount of data is <<
>> 4MB,
>> so even at the slow speeds you are saving at most a second.
>
> Only 4 MB? That's only config files and scripts or everything needed? What
> about the executable files that those scripts run? To gain any speed, those
> should be in RAM too.

As a rough approximation we need the following to gain in speed:

du -hs /etc /usr/local/etc /libexec/ /boot/modules/
2.5M    /etc
1.2M    /usr/local/etc
132k    /libexec/
4.0k    /boot/modules/

Of course, it does not make sense to load any executable into ramdisk,
because this will have a drawback once the ramdisk is discharged: the
executable will have to be remapped again from the vnode layer.
Therefore, in my opinion, only things really used at boot and only at
boot should be placed in the ramdisk. Placing the whole kernel (and
its modules) will become too expensive, and therefore I would suggest
a trim of the kernel itself.

Luca


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