2010/8/21 Lin Ming <lin@xxxxxxx>: > On Fri, Aug 20, 2010 at 8:55 AM, jean-philippe francois > <jp.francois@xxxxxxxxxx> wrote: >> Hi, >> >> Please correct me if I am sending this to the wrong list. > > LKML is better for this issue. Added. > Thank you. I have been looking at the ML archives, and it seems there has been issue related to timekeeping lately. So I tested my script with a decently recent kernel : 2.6.36-rc1. The timekeeping bug described below still exists. >> >> I would like to debug the following issue, which I suspect is related >> to cpu losing track of time when going idle. >> >> When I run the following script : >> >> #!/bin/bash >> # set hwclock to system clock to start >> # the log file with the same time >> hwclock -w >> #start with a fresh logfile >> touch clocktest.log >> echo START > clocktest.log >> while [[ true ]] >> do >> systime=$(date) >> hwtime=$(hwclock -r) >> echo "$systime | $hwtime" >> clocktest.log >> sleep 20 >> done >> >> Expected output : >> On each line, the system time (left) and hardware time (right) >> should be roughly the same. Time delta between each line should be >> around 20 seconds >> >> Observed output : >> This is an edited version of the real logfile so that it fits on one >> line. the date was removed. >> START >> 15:09:43 (UTC+0200) | 15:09:44 CEST -0.500555 secondes >> 15:10:04 (UTC+0200) | 15:10:05 CEST -1.001562 secondes >> 15:10:25 (UTC+0200) | 15:10:26 CEST -0.985944 secondes >> 15:10:46 (UTC+0200) | 15:15:46 CEST -0.032792 secondes <-- 5 minute lag ! >> 15:11:06 (UTC+0200) | 15:16:07 CEST -0.985926 secondes >> 15:11:27 (UTC+0200) | 15:16:28 CEST -1.001539 secondes >> 15:11:48 (UTC+0200) | 15:16:49 CEST -0.985969 secondes >> 15:12:09 (UTC+0200) | 15:17:10 CEST -0.985977 secondes >> 15:12:30 (UTC+0200) | 15:17:31 CEST -1.001544 secondes >> 15:12:51 (UTC+0200) | 15:17:52 CEST -0.985920 secondes >> 15:13:12 (UTC+0200) | 15:18:13 CEST -0.985939 secondes >> 15:13:33 (UTC+0200) | 15:18:34 CEST -1.001581 secondes >> 15:13:54 (UTC+0200) | 15:18:55 CEST -0.985917 secondes >> 15:14:15 (UTC+0200) | 15:29:15 CEST -0.079685 secondes <-- add >> another 10 minute >> 15:14:35 (UTC+0200) | 15:29:36 CEST -1.001568 secondes >> 15:14:56 (UTC+0200) | 15:29:57 CEST -0.985952 secondes >> >> As you can see, after 20 minutes without touching the computer, the >> system time is late by 15 minutes. >> This was tested on ubuntu 10.04 with a 2.6.32 "vanilla" kernel where >> "vanilla" means ubuntu packaged >> upstream kernel closest to the distribution shipped kernel. >> -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
