RFR(S): 8240295: hs_err elapsed time in seconds is not accurate enough

[Kevin Walls]

Oops, and with the bug ID in the title and JBS link:
https://bugs.openjdk.java.net/browse/JDK-8240295


On 02/03/2020 10:47, Kevin Walls wrote:
> Hi,
>
> (s11y and runtime opinions both relevant)
>
> A few times in the last month I've really wanted to compare the Events 
> logged in the hs_err file, and the time of the JVM's crash.
>
> "elapsed time" in hs_err is only accurate to one second, and has been 
> since before jdk5 was created.
>
> The diff below changes the format string and uses the non-rounded time 
> value (I don't see a need to change the other integer arithmetic 
> here), and we can enjoy hs_errs with detail like:
>
> ...
> Time: Mon Mar  2 09:57:13 2020 UTC elapsed time: 5.490135 seconds (0d 
> 0h 0m 5s)
> ...
>
> Thanks
> Kevin
>
>
> /jdk/open$ hg diff
> diff --git a/src/hotspot/share/runtime/os.cpp 
> b/src/hotspot/share/runtime/os.cpp
> --- a/src/hotspot/share/runtime/os.cpp
> +++ b/src/hotspot/share/runtime/os.cpp
> @@ -1016,9 +1016,8 @@
>    }
>
>    double t = os::elapsedTime();
> -  // NOTE: It tends to crash after a SEGV if we want to 
> printf("%f",...) in
> -  //       Linux. Must be a bug in glibc ? Workaround is to round "t" 
> to int
> -  //       before printf. We lost some precision, but who cares?
> +  // NOTE: a crash using printf("%f",...) on Linux was historically 
> noted here
> +  //       (before the jdk5 repo was created).
>    int eltime = (int)t;  // elapsed time in seconds
>
>    // print elapsed time in a human-readable format:
> @@ -1029,7 +1028,7 @@
>    int elmins = (eltime - day_secs - hour_secs) / secs_per_min;
>    int minute_secs = elmins * secs_per_min;
>    int elsecs = (eltime - day_secs - hour_secs - minute_secs);
> -  st->print_cr(" elapsed time: %d seconds (%dd %dh %dm %ds)", eltime, 
> eldays, elhours, elmins, elsecs);
> +  st->print_cr(" elapsed time: %f seconds (%dd %dh %dm %ds)", t, 
> eldays, elhours, elmins, elsecs);
>  }
>
>