<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="Generator" content="Microsoft Word 15 (filtered medium)"> <style></style> </head> <body lang="DE" link="blue" vlink="purple"> <div class="WordSection1"> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Thanks to everyone sharing information. Basically that’s what I expected, too, except this:<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">I run about 10 instances of the timer, and all 10 instances are started at the same second. My initial expectation wad that systemd might spread the instances in the 6 hour windows somehow.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Maybe starting the next instance once the previous instance had finished.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">I’m somewhat unsure about the energy saving: Will 10 jobs run simultaneously consume less power than the 10 jobs run sequentially? My guess is that the timer overhead may be negligible.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Regards,<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Ulrich<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p> <div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"> <div> <div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm"> <p class="MsoNormal"><b>From:</b> Adrian Vovk <adrianvovk@gmail.com> <br> <b>Sent:</b> Monday, August 19, 2024 10:45 AM<br> <b>To:</b> Andrei Borzenkov <arvidjaar@gmail.com><br> <b>Cc:</b> Barry <barry@barrys-emacs.org>; Windl, Ulrich <u.windl@ukr.de>; Systemd Devel <systemd-devel@lists.freedesktop.org><br> <b>Subject:</b> [EXT] Re: [systemd-devel] Re: Understanding the effect of AccuracySec=<o:p></o:p></p> </div> </div> <p class="MsoNormal"><o:p> </o:p></p> <div> <p>I don't have the initial email for some reason (got caught in spam filter? Idk) so I don't have the full context.<o:p></o:p></p> <div> <div> <p class="MsoNormal">On Mon, Aug 19, 2024, 03:55 Andrei Borzenkov <<a href="mailto:arvidjaar@gmail.com" target="_blank">arvidjaar@gmail.com</a>> wrote:<o:p></o:p></p> </div> <blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm"> <p class="MsoNormal">On Mon, Aug 19, 2024 at 10:11 AM Barry <<a href="mailto:barry@barrys-emacs.org" target="_blank">barry@barrys-emacs.org</a>> wrote:<br> ><br> ><br> ><br> > On 19 Aug 2024, at 06:55, Windl, Ulrich <<a href="mailto:u.windl@ukr.de" target="_blank">u.windl@ukr.de</a>> wrote:<br> ><br> ><br> > Despite of the fact that my version of systemd does not know that setting, can you explain what the effect of AccuracySec= really is?<br> ><br> ><br> > The docs <a href="https://www.man7.org/linux/man-pages/man5/systemd.timer.5.html" target="_blank"> https://www.man7.org/linux/man-pages/man5/systemd.timer.5.html</a> say this<br> ><br> > Note that this setting is primarily a power saving option<br> > that allows coalescing CPU wake-ups. It should not be<br> > confused with RandomizedDelaySec= (see below) which adds a<br> > random value to the time the timer shall elapse next and<br> > whose purpose is the opposite: to stretch elapsing of timer<br> > events over a longer period to reduce workload spikes. For<br> > further details and explanations and how both settings play<br> > together, see below.<br> ><br> > So if you have 5 timers that expire about the same time this allows them to all run at the sane time thus saving power.<br> <br> It does explain why timers are run at the same time. It does not<br> explain why "daily" + accuracy 6h runs at midnight, not close to 6am<o:p></o:p></p> </blockquote> </div> <div> <p class="MsoNormal"><o:p> </o:p></p> </div> <div> <p class="MsoNormal">When your timer is scheduled for 00:00 but accuracy is 6h, then systemd will try to fire the timer at 00:00 but is allowed to be up to 6 hours "late" to save power. So the timer will fire at any time between 00:00 and 06:00.<o:p></o:p></p> </div> <div> <p class="MsoNormal"><o:p> </o:p></p> </div> <div> <p class="MsoNormal">Let's say you have another timer set to fire at 01:00 + 6hr accuracy. systemd will likely fire both timers at around 01:00. The first timer is allowed to start anywhere between 00:00 and 06:00 and the second between 01:00 and 07:00. These ranges intersect from 01:00 to 06:00, so systemd will fire both timers at some point in that range. It's free to pick exactly when and I'm not looking at the code, but I wouldn't be surprised if it'll pick a time closer to 01:00 to minimize the amount of time it's "late".<o:p></o:p></p> <p class="MsoNormal"><o:p> </o:p></p> </div> </div> </div> </div> </body> </html>