Linux Kernel Fastboot [pdf] • Hacker News Board

Re: Linux Kernel Fastboot [pdf]

#41

Post by mycall » Sun, Sep 15, 2019, 3:49 AM UTC

Filligree wrote: post #5

jmccorm wrote: post #4

How nostalgic! Mind you, I say that in a good way! This brings me back to the heydays of Sun Microsystems where they controlled both the hardware (SPARC) and the operating system (Solaris). Sun didn't hesitate to use this to their advantage. With Clear Linux, I see Intel doing some very similar things. Yes, this was just a story about boot time, but it led me to take a look at Clear Linux and it looks like it could b…

> Anyone have some experiences with this distro (for better or worse) that they'd like to share? Not much of one, but for a while I was playing with multiple distros trying to find the best possible power management for my laptop. (XPS 13 9380.) Clear did better than the Ubuntu installation that came with it -- but a dead octopus would have done better than that . It was sitting at 6W for non-CPU-intensive work, and…

You could do further browser optimizations through about:about

Re: Linux Kernel Fastboot [pdf]

#42

Post by toast0 » Sun, Sep 15, 2019, 3:53 AM UTC

cperciva wrote: post #35

NelsonMinar wrote: post #2

I love the bit on slide 16 where initializing 8GB of RAM takes 100MS, so they boot with only 2GB and then hotplug in more memory later.

Just last weekend I was talking to one of FreeBSD's VM gurus about doing exactly this in FreeBSD too. You have to be careful about it though -- some data structures are autosized at boot, and if you're not careful you can end up with systems "running out of memory" because they have too much memory.

> some data structures are autosized at boot

It's probably a good idea to audit all the things that are autosized at boot by ram size; some of them are probably much too large on a system with 128 GB or so, given some of the sizing was written when 128 MB was big. I know I've run into the size of IP fragment buffers being way too big, but not sure what else.

Re: Linux Kernel Fastboot [pdf]

#43

Post by craftyguy » Sun, Sep 15, 2019, 3:55 AM UTC

doener wrote: post #9

Discussion on Reddit: https://www.reddit.com/r/linux/comments/d34rvg/how_intels_cl...

> Just remove the sleep(2700).

Such high quality discussion too!

Re: Linux Kernel Fastboot [pdf]

#44

Post by bmurphy1976 » Sun, Sep 15, 2019, 4:06 AM UTC

I'd really like to get my raspberry pi booting in a couple seconds. I have a few ideas for things I'd like to try but the boot time is too long. Don't need X11 but I would like to use raspbian.

Re: Linux Kernel Fastboot [pdf]

#45

Post by why-oh-why » Sun, Sep 15, 2019, 4:10 AM UTC

craftyguy wrote: post #43

doener wrote: post #9

Discussion on Reddit: https://www.reddit.com/r/linux/comments/d34rvg/how_intels_cl...

> Just remove the sleep(2700). Such high quality discussion too!

> SATA driver init takes 100 to 200 ms even without a real disk

While it’s a joke, they’re not particularly far from the truth, as noted in a different comment here. They do indeed wait for some parts to respond.

Re: Linux Kernel Fastboot [pdf]

#46

Post by l3s2d » Sun, Sep 15, 2019, 4:20 AM UTC

mises wrote: post #20

I've seriously got to look into running arch with a clear linux kernel. I knew they did some pretty serious optimization work, but this is definitely impressive.

Some relevant links: https://aur.archlinux.org/packages/linux-clear/ https://www.reddit.com/r/archlinux/comments/7rcvxc/clear_lin...

Re: Linux Kernel Fastboot [pdf]

#47

Post by BeeOnRope » Sun, Sep 15, 2019, 4:37 AM UTC

aidenn0 wrote: post #30

lonelappde wrote: post #15

Earlier quoted context omitted.

That's a good way to estimate but not appropriate for comparing to powertop, due to overhead. Also "50%" of energy is an estimate based on voltage, not actually energy usage. That's why Apple has stopped showing percentages in their OSes. You should use the same methodology for both.

I thought most laptop batteries use coulomb counting rather than voltage for estimating battery level?

Yes, any decent laptop for sure uses coulomb counting, not a simple voltage measurement.

Re: Linux Kernel Fastboot [pdf]

#48

Post by swiley » Sun, Sep 15, 2019, 4:37 AM UTC

ComputerGuru wrote: post #33

Filligree wrote: post #12

Earlier quoted context omitted.

I used Powertop on Linux, yes. For Windows, I simply let the laptop run until it had used 50% of the battery. Watts = Joules / second. On Linux, I used the same methodo to calibrate against powertop. (But found less than 5% of discrepancy anyway.)

The only valid approach is to remove the battery and plug it into a kill-a-watt or similar.

Many laptops aren’t stable at full speed without a battery.

Re: Linux Kernel Fastboot [pdf]

#49

Post by ComputerGuru » Sun, Sep 15, 2019, 4:43 AM UTC

swiley wrote: post #48

ComputerGuru wrote: post #33

Earlier quoted context omitted.

The only valid approach is to remove the battery and plug it into a kill-a-watt or similar.

Many laptops aren’t stable at full speed without a battery.

I’m not aware of anything other than a MacBook or some micro ultra books that do that because they try to keep the power brick size down. Any device with a user-removable battery should be able to do that, provided you’re using an adapter that provides sufficient current.

Re: Linux Kernel Fastboot [pdf]

#50

Post by amluto » Sun, Sep 15, 2019, 4:43 AM UTC

newnewpdro wrote: post #14

> Systemd is ~1.5MB - the loading time for emmc is 100ms Surely not all of systemd is faulted in immediately, is this really an issue?

If you want just the important parts faulted in, you need to get the important parts into their own pages, preferably in order. I don’t know whether profile-guided linking is a thing.