On Tue, 18 Jul 2017, Mark Salyzyn wrote: > On 07/18/2017 03:35 PM, Thomas Gleixner wrote: > > There was some discussion about making the clock source for dmesg time > > stamps selectable, so you can use MONOTONIC, REALTIME, BOOTTIME. The > > patches looked sensible, but there was some showstopper vs. the user space > > dmesg utility. See: > > The timestamps are useful for the 'second' purpose of these patches when > dmesg time is BOOTTIME or MONOTONIC, and can be turned off if REALTIME > is selected. Having rtc_show_time a single point for switching this no doubt > helps, > not hinders, that dmesg issue. > > The inflection points would still serve a purpose, still need > suspend/resume/hibernate/restore. The reboot messages are _only_ useful to > us with their timestamps, as I checked and the only tools that use those are > for log synchronization. We may be able to do away with them on REALTIME > dmesg'ing; but the standardization of the message as a marker would have a > legacy purpose (!) > > NB: We have a similar configuration for the user space logger, which can be > configured to report in MONOTONIC time. We have yet to have a vendor > use the feature, opting for REALTIME logging for user space activities. > Our klogd (which runs at background priority and is batched) manages a > histogram relationship between MONOTONIC and REALTIME helped by these > prints and incorporates the REALTIME dmesg logs merged into our user > space logging database. There is another option to remedy this and the dmesg tooling issues: Instead of switching the time stamps in dmesg to a different clock we might as well have an optional secondary timestamp. So instead of: [ 341.590930] wlan0: associated you would get: [ 341.590930] [ sec.usec] wlan0: associated where the second time stamp would be CLOCK_REALTIME/BOOTTIME. That should also solve Prarits problem, hmm? Thanks, tglx
