Bug 204748
Summary: | ntp wakes up once per second, that's overkill | ||
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Product: | [Fedora] Fedora | Reporter: | Arjan van de Ven <arjan> |
Component: | ntp | Assignee: | Miroslav Lichvar <mlichvar> |
Status: | CLOSED RAWHIDE | QA Contact: | Brian Brock <bbrock> |
Severity: | medium | Docs Contact: | |
Priority: | medium | ||
Version: | rawhide | CC: | redhat |
Target Milestone: | --- | ||
Target Release: | --- | ||
Hardware: | All | ||
OS: | Linux | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2007-01-29 14:01:41 UTC | Type: | --- |
Regression: | --- | Mount Type: | --- |
Documentation: | --- | CRM: | |
Verified Versions: | Category: | --- | |
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
Cloudforms Team: | --- | Target Upstream Version: | |
Embargoed: | |||
Bug Depends On: | |||
Bug Blocks: | 204948 |
Description
Arjan van de Ven
2006-08-31 12:35:00 UTC
Actually system clock isn't corrected in user space at all when PLL updates in kernel are used, so 16s would be ok in this regard. But there is other code that needs to be executed with better accuracy than 16s, just changing EVENT_TIMEOUT isn't sufficient. However, I think it is possible to modify ntpd so that it will wake up just few times per hour in usual conditions. I will check how much code needs to be modified. Any updates? This wakeup issue definitely burns power. Fixed in ntp-4.2.4-4.fc7. Note that ntpd still needs to wake up once per second when a refclock is used (i.e. server 127.127.*.*) or kernel discipline is disabled. It's not clear to me how comment #3 applies to typical systems. On this Fedora 7 machine which so far as I know doesn't have a reference clock, NTP still wakes up once a second showing as do_adjtimex (sync_cmos_clock) which sounds to me like it's scribbling into the battery backed clock, certainly not something we want to waste our time doing frequently. I have ntp-4.2.4p2-3.fc7 How would I know if "kernel discipline is disabled" ? The Local Clock (server 127.127.1.0) is also a reference clock. It was enabled by default in ntp.conf before F7. Kernel discipline should be always enabled unless ntpd is started with -x option or it's disabled in ntp.conf with tinker command. ntptime prints PLL in the clock status line. To verify that ntpd isn't causing the wakeups directly you can start ntpd with -D 4 and watch the output. OK, powertop still blames NTP for one wakeup per second but it appears from strace output that this is caused in fact by NTP calling adjtimex() once every minute or so, presumably some kernel code then does... something once per second. Micro-adjustments to the clock? I don't know if kernel wakeups are less horrible than userspace wakeups but I'm content that NTP waking up once per minute or so is acceptable, this bug was properly closed and I will leave you alone, sorry for the disturbance. one thing to note; if you upgraded from a previous version of fedora, there is a /etc/ntp.conf.rpmnew, which you need to copy over /etc/ntpd.conf to have these changes effected. Please file a bug against kernel component. I'm not sure, but I think I've seen a similar problem while playing with different timesources. |