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Linux Kernel Fastboot [pdf]

linuxplumbersconf.org

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Re: Linux Kernel Fastboot [pdf]

#31

Post by loki49152 »

bt848 wrote: post #23
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…

Booting a Sun in the 90s took so long that we had the janitor go and power up the CAD lab half an hour before anyone got to the office. Whatever you are nostalgic for wasn’t a Sun.

Our Sun lab ran on SunOS 4.1.1. Its NFS implementation was so unstable we'd get perhaps an hour and a half of use at a stretch before the file server would reboot... on an 8 machine network.

Re: Linux Kernel Fastboot [pdf]

#32

Post by trdtaylor1 »

sedatk wrote: post #28
zamadatix wrote: post #22

> “mem=4096m” in cmdline to only init 2 GB What is going on that makes this 2:1?

2gb user + 2gb kernel?

2 gb user + 1 gb swap + 1 gb rootfs unpacked in ram perhaps. They discuss a decompression operation and the only portion of the sequence that would occur in normally is unpacking a rootfs in RAM.

Re: Linux Kernel Fastboot [pdf]

#33

Post by ComputerGuru »

Filligree wrote: post #12
voltagex_ wrote: post #11

Earlier quoted context omitted.

How did you measure the power usage on Windows? I'm assuming you used Powertop on Linux.

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.

Re: Linux Kernel Fastboot [pdf]

#34

Post by cperciva »

cocoa19 wrote: post #25
cperciva wrote: post #3

Those of you who are interested in such things might also like to watch my BSDCan 2018 talk: https://www.youtube.com/watch?v=HMywejyXB9k

Sorry for off-topic: I checked your HN profile and tarsnap looks like what I've been searching for a long time. Looks much more straight forward than nextcloud and open source too. Wish you success with your company.

Thanks!

Re: Linux Kernel Fastboot [pdf]

#35

Post by cperciva »

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.

Re: Linux Kernel Fastboot [pdf]

#36

Post by ComputerGuru »

jtchang wrote: post #16

> SATA driver init takes 100 to 200 ms even without a real disk That's pretty interesting. Wonder what it is doing?

SATA controller firmware has a hard-coded “drive predelay” that waits before enumerating attached devices, a relic from the days long before SSDs. Even when an option to set a custom amount is available in the BIOS, it is in addition to and not instead of, as there’s no bus master to tell it all attached disks have init and the controller may speak to them.

It wouldn’t necessarily have to be done synchronously up front at all, except when the BIOS hands off control of the system to the SATA controller it expects that afterward it has a definitive list of available boot devices and their properties, for selection/display in the boot menu and BIOS configuration.

Theoretically with UEFI and it’s NVRAM-resident settings, a boot device could be expressed as a namespace and path, and the firmware need not enumerate devices until it has determined that there’s a need to search for alternative/fallback boot devices, but the stack hasn’t been updated with that in mind.

Re: Linux Kernel Fastboot [pdf]

#37

Post by ComputerGuru »

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.

Most of the bloat isn’t from the kernel. That’s the last thing you really optimize after getting rid of all the background services, startup tasks, etc.

Re: Linux Kernel Fastboot [pdf]

#38

Post by throwaway8941 »

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.

Reminds me of Windows 95 "running out of memory" on systems with too much RAM.

https://devblogs.microsoft.com/oldnewthing/20030814-00/?p=42...

Re: Linux Kernel Fastboot [pdf]

#40

Post by tvst »

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…

Clear Linux is blazing fast (compiled with Intel compilers), and supposedly has a strong security model -- but it also has an extremely limited package selection. To the point that it's just not usable for me.

Also, its package manager forces you to install "bundles" of somewhat related packages rather than just the specific packages you want and their deps. Maybe I'm missing something, but I find this very odd.

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