On Mon, Aug 28, 2017 at 01:31:31AM +0100, Ben Hutchings wrote: > > OTOH, the list of required modules may be small enough for us to > > enumerate the ones we need for booting in /etc/initramfs-tools/modules. > > ...and then you could use MODULES=list. initramfs-tools will still > follow module static dependencies in this case. > > > I will look into this, and we'll see what it does to boot times. > > Note that the saving will mainly be in time to load the initramfs - > which on Google Compute Engine is done through BIOS disk services that > have very low performance. The mere presence of the unneeded modules > in the initramfs won't cause them to be loaded into the kernel and > shouldn't make much difference to the time taken to boot after this > point. On Amazon's HVM instance families, the initramfs is read from "local" disk, which may be network-attached or actually local. I haven't profiled load times in great depth, but my guess is that reading and uncompressing the image would be the biggest contributors to the load time. In my experimentation, uncompressing an 18 MB initramfs takes roughly 500 ms of clock time when read from network storage. That's not completely insignificant, but considering the fragility of MODULES=list or MODULES=dep, I'm not sure it's the best place to look for optimizations right now. noah
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