5 ms·

That 0.7s boot from bios to desktop is impressive.

arghwhat 3y ago
Intel had a talk a few years back where they got Linux boot down to 0.3s from power is applied to fully interactive UI on an embedded platform. That case was meant for automotive, where you want things like infotainment and instrument cluster available shortly after the accessory power is enabled.
- kwhitefoot 3y ago
  So why do we have to wait so long for other versions to boot?
  - rizky05 3y ago
    [dead]
  - yjftsjthsd-h 3y ago
    A lot of it is hardware startup and enumeration, and also software services (because they had to really strip it down to get there). I'm more curious why my car, which is fairly recent, doesn't start in 0.3s.
    - pmarreck 3y ago
      There should be a key you can hold down which would mean "skip all enumeration and assume everything is exactly as it was the last time you booted" (with a brief warning to the user about the possible risks introduced by this)
      - yjftsjthsd-h 3y ago
        If we're going that route, I'd like a bootloader-supplied kernel option that defaults to enabled (ideally with the GRUB/whatever menu having am option to disable it.
        pmarreck 3y ago
        That's fair. I just wanted it to default to safe (as good user design dictates).
    - wannacboatmovie 3y ago
      A typical car is broken down into many small, dedicated computers. The powertrain and body control modules, assuredly running a RTOS, certainly do. The PCM for example controls when the spark plugs fire. If it did not boot instantly, the engine wouldn't run. If the BCM didn't boot, the doors wouldn't unlock nor would the key or PTS start the engine. The user-facing infotainment crap is not necessary for the "car" part to function. You could physically remove it and the car would still be drivable.
  - TkTech 3y ago
    If you turn off quiet boot, you'll see an impressive list of things getting started up, many of which the kernel isn't in full control of. DHCP (sometimes), gpus, NTP, disk decryption, TPM, monitor probing, USB hub enumeration, on and on.
    - kwhitefoot 3y ago
      But all the stuff that is actually necessary is the same on every boot so no enumeration and probing should be necessary.
      - TkTech 3y ago
        Is it? My laptop is only shutoff when switching from a dock at home to a dock at work, changing the GPU and hubs available. The OS I just netbooted off my NAS has no idea what it's booting on. I can plug and unplug USB devices anytime, including while the system is off. Maybe I swapped USB headsets, maybe I plugged in a fingerprint or smartcard reader, which needs to be initialized before the login manager starts. Maybe my time server is no longer reachable, so NTP needs to find a new one from the pool, because if it doesn't sync timing correctly the certificate for LDAP won't validate and my work laptop won't be able to login. Maybe it needs to initialize the networking stack to handle an NFS or Samba mount in my /etc/fstab which has a nowait=0, since I use it as a boot volume. This could be a very, very long list of hypothetical changes :)
        bmicraft 3y ago
        pxe boot obviously has some constraints that don't usually apply otherwise. Presumably the dock can be detached while booted, so the kernel should also be able to handle booting and only detect at some point that the dock has disappeared
        xp84 3y ago
        All that USB stuff ought not to be blocking though, right? since those can also be connected or removed at any time.
      - 3y ago
  - bee_rider 3y ago
    You can see what is eating up the time as you boot if you use SystemD. https://wiki.archlinux.org/title/Improving_performance/Boot_process https://wiki.archlinux.org/title/Improving_performance/Boot_... I haven’t really had any issues with Linux boot times for personal machines lately. I think the people that care most about getting into the sub-second range are the ones doing cloud VM stuff, spinning up lots of micro services or whatever.
    - jeroenhd 3y ago
      My computer takes about 45 seconds to start, which isn't terrible, but when I run a Windows XP VM on a quarter of the CPU cores I'm reminded of how long those 45 seconds are. Even without the stupid 20 seconds of firmware I can't do anything about, XP shows me an interactive desktop in half the time Linux does. Windows 7 is just as fast, and just as fully-featured as my desktop Linux install. Windows 11 still boots faster (and more reliably) than Linux despite the overhead of Windows Defender and drive signature checking. I don't need 0.3 seconds of boot time on my desktop, but something a bit faster would be nice. I think my machine is so slow by the death of a thousand services all starting at boot.
      - bee_rider 3y ago
        Have you tried running systemd-analyze And then systemd-analyze critical-chain To see what is slowing it down? My system takes 10 seconds to boot apparently, with fairly minimal tuning (I boot from a USB drive so I try not to worry too much about this, hah!). But I don’t use a desktop environment or any of that sort of stuff, so it is probably not a good comparison. Still, 45 seconds is pretty slow, I wonder if it is waiting for something that idles out; network interfaces or something like that.
        jeroenhd 3y ago
        20 seconds in firmware, 8 in kernel, 6 seconds waiting for systemd networks to load, a second for Docker and an encrypted LUKS drive are most of my boot process (and a thousand tiny systemd services, of course). I can disable a few things here and there, but whatever hardware detection takes place in the kernel (I assume Nvidia related things, it's always Nvidia it seems) isn't really somethint I can change. I can try disabling more POST parts, maybe, and disable Docker on boot to take off another second, but to shave everything down I'll probably need to reinstall.
  - arghwhat 3y ago
    On many machines, the firmware is the largest contributor, with user-space services and their dependencies being the rest. `systemd-analyze` (in particular, `systemd-analyze critical-chain` and `systemd-analyze plot > plot.svg`) are useful to diagnose. On my system you can see that my graphical session waits for systemd-user-session.service, which waits for network.target, which waits for NetworkManager taking its sweet time, which isn't started before network-pre which waits until nftables is done loading rules, etc. Optimizing the service order and their dependencies does wonders for boot time.
    - kwhitefoot 3y ago
      > Optimizing the service order and their dependencies does wonders for boot time. Why isn't this automatic? I'm pretty sure most of us have neither expertise not enthusiasm for that job.
      - bmicraft 3y ago
        It is automatic, but systemd obviously is constrained by the dependencies specified inside the unit files (that's kinda the point). The real question would be, why can't NetworkManager handle being started before everything is initialized. In turn the answer is probably "because it's hard"
      - monocasa 3y ago
        I mean, it is, within the rule set specified by the config files. Distros just tend to explicitly default to the system being more fully up before presenting an interactive GUI because a lot of users' workflows expect that.
      - arghwhat 3y ago
        It is a matter of requirements. A login may require LDAP or Kerberos, which requires network connectivity. Pulling up network before the firewall is initialized could be dangerous. Maybe your desktop environment needs to play a jingle, so it by default waits for sound to init. Service optimization is basically deciding what your system doesn't need in order to function for your usage, and moving things you don't need to a late initialization with no dependents. A distribution dedicated for a particular machine usage and desktop environment could do some tuning on your behalf, but it is not generic.
  - squarefoot 3y ago
    OSes not tailored for generic platforms can be built without all that conditional code that executes whenever this or that chipset is found; then all those delays because you don't know how much time a chipset or peripheral will take to initialize, etc.
  - joshmarinacci 3y ago
    Read up on “raspberry pi fast boot” and you’ll learn a lot about the tricks that can be used for fast booting, and also why they aren’t the default.

Intel had a talk a few years back where they got Linux boot down to 0.3s from power is applied to fully interactive UI on an embedded platform. That case was meant for automotive, where you want things like infotainment and instrument cluster available shortly after the accessory power is enabled.

kwhitefoot 3y ago
So why do we have to wait so long for other versions to boot?
- rizky05 3y ago
  [dead]
- yjftsjthsd-h 3y ago
  A lot of it is hardware startup and enumeration, and also software services (because they had to really strip it down to get there). I'm more curious why my car, which is fairly recent, doesn't start in 0.3s.
  - pmarreck 3y ago
    There should be a key you can hold down which would mean "skip all enumeration and assume everything is exactly as it was the last time you booted" (with a brief warning to the user about the possible risks introduced by this)
    - yjftsjthsd-h 3y ago
      If we're going that route, I'd like a bootloader-supplied kernel option that defaults to enabled (ideally with the GRUB/whatever menu having am option to disable it.
      - pmarreck 3y ago
        That's fair. I just wanted it to default to safe (as good user design dictates).
  - wannacboatmovie 3y ago
    A typical car is broken down into many small, dedicated computers. The powertrain and body control modules, assuredly running a RTOS, certainly do. The PCM for example controls when the spark plugs fire. If it did not boot instantly, the engine wouldn't run. If the BCM didn't boot, the doors wouldn't unlock nor would the key or PTS start the engine. The user-facing infotainment crap is not necessary for the "car" part to function. You could physically remove it and the car would still be drivable.
- TkTech 3y ago
  If you turn off quiet boot, you'll see an impressive list of things getting started up, many of which the kernel isn't in full control of. DHCP (sometimes), gpus, NTP, disk decryption, TPM, monitor probing, USB hub enumeration, on and on.
  - kwhitefoot 3y ago
    But all the stuff that is actually necessary is the same on every boot so no enumeration and probing should be necessary.
    - TkTech 3y ago
      Is it? My laptop is only shutoff when switching from a dock at home to a dock at work, changing the GPU and hubs available. The OS I just netbooted off my NAS has no idea what it's booting on. I can plug and unplug USB devices anytime, including while the system is off. Maybe I swapped USB headsets, maybe I plugged in a fingerprint or smartcard reader, which needs to be initialized before the login manager starts. Maybe my time server is no longer reachable, so NTP needs to find a new one from the pool, because if it doesn't sync timing correctly the certificate for LDAP won't validate and my work laptop won't be able to login. Maybe it needs to initialize the networking stack to handle an NFS or Samba mount in my /etc/fstab which has a nowait=0, since I use it as a boot volume. This could be a very, very long list of hypothetical changes :)
      - bmicraft 3y ago
        pxe boot obviously has some constraints that don't usually apply otherwise. Presumably the dock can be detached while booted, so the kernel should also be able to handle booting and only detect at some point that the dock has disappeared
      - xp84 3y ago
        All that USB stuff ought not to be blocking though, right? since those can also be connected or removed at any time.
    - 3y ago
- bee_rider 3y ago
  You can see what is eating up the time as you boot if you use SystemD. https://wiki.archlinux.org/title/Improving_performance/Boot_process https://wiki.archlinux.org/title/Improving_performance/Boot_... I haven’t really had any issues with Linux boot times for personal machines lately. I think the people that care most about getting into the sub-second range are the ones doing cloud VM stuff, spinning up lots of micro services or whatever.
  - jeroenhd 3y ago
    My computer takes about 45 seconds to start, which isn't terrible, but when I run a Windows XP VM on a quarter of the CPU cores I'm reminded of how long those 45 seconds are. Even without the stupid 20 seconds of firmware I can't do anything about, XP shows me an interactive desktop in half the time Linux does. Windows 7 is just as fast, and just as fully-featured as my desktop Linux install. Windows 11 still boots faster (and more reliably) than Linux despite the overhead of Windows Defender and drive signature checking. I don't need 0.3 seconds of boot time on my desktop, but something a bit faster would be nice. I think my machine is so slow by the death of a thousand services all starting at boot.
    - bee_rider 3y ago
      Have you tried running systemd-analyze And then systemd-analyze critical-chain To see what is slowing it down? My system takes 10 seconds to boot apparently, with fairly minimal tuning (I boot from a USB drive so I try not to worry too much about this, hah!). But I don’t use a desktop environment or any of that sort of stuff, so it is probably not a good comparison. Still, 45 seconds is pretty slow, I wonder if it is waiting for something that idles out; network interfaces or something like that.
      - jeroenhd 3y ago
        20 seconds in firmware, 8 in kernel, 6 seconds waiting for systemd networks to load, a second for Docker and an encrypted LUKS drive are most of my boot process (and a thousand tiny systemd services, of course). I can disable a few things here and there, but whatever hardware detection takes place in the kernel (I assume Nvidia related things, it's always Nvidia it seems) isn't really somethint I can change. I can try disabling more POST parts, maybe, and disable Docker on boot to take off another second, but to shave everything down I'll probably need to reinstall.
- arghwhat 3y ago
  On many machines, the firmware is the largest contributor, with user-space services and their dependencies being the rest. `systemd-analyze` (in particular, `systemd-analyze critical-chain` and `systemd-analyze plot > plot.svg`) are useful to diagnose. On my system you can see that my graphical session waits for systemd-user-session.service, which waits for network.target, which waits for NetworkManager taking its sweet time, which isn't started before network-pre which waits until nftables is done loading rules, etc. Optimizing the service order and their dependencies does wonders for boot time.
  - kwhitefoot 3y ago
    > Optimizing the service order and their dependencies does wonders for boot time. Why isn't this automatic? I'm pretty sure most of us have neither expertise not enthusiasm for that job.
    - bmicraft 3y ago
      It is automatic, but systemd obviously is constrained by the dependencies specified inside the unit files (that's kinda the point). The real question would be, why can't NetworkManager handle being started before everything is initialized. In turn the answer is probably "because it's hard"
    - monocasa 3y ago
      I mean, it is, within the rule set specified by the config files. Distros just tend to explicitly default to the system being more fully up before presenting an interactive GUI because a lot of users' workflows expect that.
    - arghwhat 3y ago
      It is a matter of requirements. A login may require LDAP or Kerberos, which requires network connectivity. Pulling up network before the firewall is initialized could be dangerous. Maybe your desktop environment needs to play a jingle, so it by default waits for sound to init. Service optimization is basically deciding what your system doesn't need in order to function for your usage, and moving things you don't need to a late initialization with no dependents. A distribution dedicated for a particular machine usage and desktop environment could do some tuning on your behalf, but it is not generic.
- squarefoot 3y ago
  OSes not tailored for generic platforms can be built without all that conditional code that executes whenever this or that chipset is found; then all those delays because you don't know how much time a chipset or peripheral will take to initialize, etc.
- joshmarinacci 3y ago
  Read up on “raspberry pi fast boot” and you’ll learn a lot about the tricks that can be used for fast booting, and also why they aren’t the default.