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

Warner Losh imp at bsdimp.com
Wed Aug 21 08:39:49 PDT 2013


On Aug 21, 2013, at 12:31 AM, Luca Ferrari wrote:

> 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.

The kernel *NEVER* makes sense on a ram disk. It is already loaded into memory...

And you're talking about 4MB of data, or < 1s of waiting for the disk to deliver it.

Warner


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