8234397: add OS uptime information to os::print_os_info output

[David Holmes]

Hi Matthias,

On 4/12/2019 1:38 am, Baesken, Matthias wrote:
> Hi David,  here is a new webrev   based on  your comments :
> 
> http://cr.openjdk.java.net/~mbaesken/webrevs/8234397.4/

Thanks for the updates.

>>
>> Is %llu supported by all compilers (32-bit as well)?
>>
> 
> Not sure , I checked and  it works  with VS2017/32bit.  But I don't know about other compilers.    So I better use long / %ld.

I think int would be fine - 2^31 seconds is a long time.

> 
> Btw I noticed that
> 
> os::print_date_and_time
>   ...
>   // print elapsed time in a human-readable format:
> 
> Contains  very similar coding  to  what I do in os::print_dhm  -->  should this maybe be unified ?

I don't really see a way to unify. You might hoist the constants out to 
be static in the file for sharing:

   const int secs_per_day  = 86400;
   const int secs_per_hour = 3600;
   const int secs_per_min  = 60;

and add others as needed.

Thanks,
David

> 
> Best regards, Matthias
> 
> 
> 
>> Hi Matthias,
>>
>> On 29/11/2019 11:58 pm, Baesken, Matthias wrote:
>>> Hi, here is a new webrev,  this time with nicer  output  (see os.cpp) .
>>>
>>> http://cr.openjdk.java.net/~mbaesken/webrevs/8234397.3/
>>
>> src/hotspot/os/bsd/os_bsd.cpp
>>
>> This link may be more general than the Apple "iOS" one.
>>
>> https://man.openbsd.org/sysctl.2
>>
>> +    time_t bootsec = boottime.tv_sec, currsec = time(NULL);
>>
>> Please write the two declarations on separate lines.
>>
>> ---
>>
>> src/hotspot/os/posix/os_posix.cpp
>>
>> + // unfortunately it does not work on macOS
>>
>> Still no mention of Linux
>>
>> ---
>>
>> src/hotspot/share/runtime/os.cpp
>>
>> +   if (minutes < 10) {
>> +     st->print_cr("%s %llu days %llu:0%llu hours", startStr, days,
>> hours, minutes);
>> +   } else {
>> +     st->print_cr("%s %llu days %llu:%llu hours", startStr, days,
>> hours, minutes);
>> +   }
>>
>> You should just use a zero-padded width of 2 to get 01..09 for minutes.
>>
>> Is %llu supported by all compilers (32-bit as well)?
>>
>> ---
>>
>> src/hotspot/os/windows/os_windows.cpp
>>
>> +  unsigned long long ticks = GetTickCount64();
>> +  os::print_dhm(st, "OS uptime:", ticks);
>>
>> GetTickCount64 returns milliseconds since boot not seconds.
>>
>> ---
>>
>> Thanks,
>> David
>>
>