On Sat 2018-12-01 23:44:37, Tetsuo Handa wrote: > On 2018/12/01 0:40, Petr Mladek wrote: > >> Some examples for console output: > >> > >> [ 0.293000] [T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ > >> 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) > >> [ 0.299733] [T1] Performance Events: Haswell events, core PMU driver. > >> [ 2.813808] [T35] clocksource: Switched to clocksource tsc > >> [ 2.893984] [C0] random: fast init done > > ^ > > > > Please, remove the space between the timestamp and the from field. > > This space was emitted by print_time(). Do we want to modify print_time() > not to emit this space if the from field is printed?
Exactly. This is what I thought about. > If we modify print_time(), I think that the leading spaces inserted by "%5lu" > makes little sense, for "%5lu" is too small for systems with uptime >= 1.16 > days > and parsers after all cannot assume fixed length for the timestamp field. > Then, > we could change from "%5lu.%06lu" to "%lu.%06lu" so that parsers (like > /bin/awk) > can get prefix part using white spaces as a delimiter. My primary concern was a human readability. The different header columns are separated by brackets and the message itself is separated by the space. awk could easily use \[ as the separator. But you made a good point about the column width. The text might be hard to read when every line of text starts on a different column. And the might be bigger differences for the task id. It might be useful to add some reasonable default width also for the for the "from_id" column. > If we want to reduce space, do we want to do like > > [0.293000@T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz > (family: 0x6, model: 0x3c, stepping: 0x3) > [0.299733@T1] Performance Events: Haswell events, core PMU driver. > [2.813808@T35] clocksource: Switched to clocksource tsc > [2.893984@C0] random: fast init done Hmm, this is pretty hard to parse by my eyes. Also it changes the format of the timestamp column. I think that the following might give the best human user experience: [ 0.293000][ T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) [ 0.299733][ T1] Performance Events: Haswell events, core PMU driver. [ 2.813808][ T35] clocksource: Switched to clocksource tsc [ 2.893984][ C0] random: fast init done > >> @@ -1037,6 +1054,9 @@ void log_buf_vmcoreinfo_setup(void) > >> VMCOREINFO_OFFSET(printk_log, len); > >> VMCOREINFO_OFFSET(printk_log, text_len); > >> VMCOREINFO_OFFSET(printk_log, dict_len); > >> +#ifdef CONFIG_PRINTK_FROM > >> + VMCOREINFO_OFFSET(printk_log, from_id); > >> +#endif > > > > The crash tool would need to be updated if anyone wanted to read > > the log from the extended structure. Well, it might be done later > > if people start using it more widely. > > Since syzbot can utilize output from only normal consoles, I can > keep extended records unmodified for now. Please, add VMCOREINFO_OFFSET(printk_log, from_id) so that crashdump can be updated when necessary. > > > > I think about adding one more filed "u8 version". It would help > > to solve the external compatibility in the long term. > > /dev/kmsg format allows adding more fields, but that format did not define > how to tell what fields are there. If fields are conditionally added by > kernel config options, I don't think that "u8 version" field helps. > Unless we add fields unconditionally, we will need to use $name=$value > (where $name and $value must not contain ',' and ';') representation. /dev/kmsg uses key=value notation. It does not need any version. The version filed was intended for crashdump. It would make the life easier for its maintainers. Well, I do not resist on it. Let's put the version field aside for now. Best Regards, Petr
