Re: [systemd-devel] Reduce loading time (size) of init program (systemd)
On Mon, Sep 23, 2019 at 05:37:34PM -0700, Auke Kok wrote: > > On 9/16/19 7:14 AM, Paul Menzel wrote: > >In his talk*Linux kernel fastboot on the way* at this years Linux > >Plumbers Conference [1][2], Feng Tang (CCed) has the notes below on > >the slide for userspace/systemd. > > > >>• Systemd is ~1.5MB - the loading time for emmc is 100ms> • Can we use a > >>small lightweight “init” program, which starts > >> target programs in parallel and readahead to preload libraries > >> and executables? > >Are you already aware of these issues? If yes, have you ideas or > >suggestions how to solve this? Maybe something to discuss at this > >weeks All System Go! 2019. > > Chiming in here > > The benefits of doing that often don't outweigh the cost. Readahead is > *difficult* and very much impossible to get right for a generic situation, > so in many cases it has stopped being used. The only place e.g. ClearLinux > uses it now is for targeted use cases where it makes sense (in our case, the > desktop, because GNOME is ... monstrous). For typical cloud and bare metal > situations and even VM instances, readahead doesn't appear to be useful at > all. Thanks Auke for the detailed explanation! I agree this is a problem between general solution vs specific HW/requirement, and also a balance between the 100ms and extra complexity (plus maintaining effort). I think it is worth trying for your own product if it really cares about the 100 ms. My colleagues did added some codes to get the time back, but the codes are too hacky and platform specific to be upstreamed. Thanks, Feng > > Despite loading time for eMMC being 100ms, I've not seen the actual loading > time of systemd be an issue. The worst thing at boot that can happen is that > some process starts writing a lot (journal rotating, for instance), and is > far more detrimental to boot time from my experience. > > I like Feng's slides, but, it's not the first time that things were proposed > that didn't pan out as much as we thought it did. > > Auke > > ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Reduce loading time (size) of init program (systemd)
On 9/16/19 7:14 AM, Paul Menzel wrote: In his talk*Linux kernel fastboot on the way* at this years Linux Plumbers Conference [1][2], Feng Tang (CCed) has the notes below on the slide for userspace/systemd. • Systemd is ~1.5MB - the loading time for emmc is 100ms> • Can we use a small lightweight “init” program, which starts target programs in parallel and readahead to preload libraries and executables? Are you already aware of these issues? If yes, have you ideas or suggestions how to solve this? Maybe something to discuss at this weeks All System Go! 2019. Chiming in here The benefits of doing that often don't outweigh the cost. Readahead is *difficult* and very much impossible to get right for a generic situation, so in many cases it has stopped being used. The only place e.g. ClearLinux uses it now is for targeted use cases where it makes sense (in our case, the desktop, because GNOME is ... monstrous). For typical cloud and bare metal situations and even VM instances, readahead doesn't appear to be useful at all. Despite loading time for eMMC being 100ms, I've not seen the actual loading time of systemd be an issue. The worst thing at boot that can happen is that some process starts writing a lot (journal rotating, for instance), and is far more detrimental to boot time from my experience. I like Feng's slides, but, it's not the first time that things were proposed that didn't pan out as much as we thought it did. Auke ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] Reduce loading time (size) of init program (systemd)
Dear systemd folks, In his talk *Linux kernel fastboot on the way* at this years Linux Plumbers Conference [1][2], Feng Tang (CCed) has the notes below on the slide for userspace/systemd. > • Systemd is ~1.5MB - the loading time for emmc is 100ms> • Can we use a > small lightweight “init” program, which starts > target programs in parallel and readahead to preload libraries > and executables? Are you already aware of these issues? If yes, have you ideas or suggestions how to solve this? Maybe something to discuss at this weeks All System Go! 2019. Kind regards, Paul [1]: https://linuxplumbersconf.org/event/4/contributions/281/ [2]: https://linuxplumbersconf.org/event/4/contributions/281/attachments/216/617/LPC_2019_kernel_fastboot_on_the_way.pdf smime.p7s Description: S/MIME Cryptographic Signature ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
