RFR: 8151526: Print -Xlog configuration in the hs_err_pid file

[Thomas Stüfe]

Hi Marcus,

sorry for the delay.

On Fri, Apr 1, 2016 at 10:45 AM, Marcus Larsson <marcus.larsson at oracle.com>
wrote:

> Hi,
>
> On 03/31/2016 08:08 PM, Max Ockner wrote:
>
> (Replies in line)
>
> On 3/30/2016 9:31 AM, Thomas Stüfe wrote:
>
> Hi Max,
>
> Disclaimer: not a (R)eviewer.
>
> Do we really need a list of all tags and all decorators?
>
> Just going by what we currently put in the hs_err file, I think this may
> be the first "Do we really need" we've ever asked for this type of change.
>
> All joking aside, I think it is a good idea to direct users toward proper
> UL usage whenever we have a chance.
>
> Also: I assume what you print is the Log state as it is at the time the
> hs-err file is printed. If logging was enabled/changed during lifetime of
> the VM, e.g. with jcmd, would it be possible to see that? At least a
> warning if logging was not enabled from the start on.
>
> Would it be possible? Yes, but I think this would require a framework
> change. It does not look like any marks are made when the LogConfiguration
> changes during runtime, and we would need to record that in order to know
> what to print when we dump into hs_err.
>
>
> Yes, this would required the framework to keep some sort of log of
> configuration changes. Is there value in knowing that the log configuration
> changed since startup?
>
>
I think the only reason to print the log configuration is that we can find
the associated log output and interpret it. I guess most supporters would
assume that the log configuration in the hs-err file was active the whole
process life. If it was not, the supporter may interpret missing output
somehow ("I did not see my trace line so it did not happen"). So I think it
makes sense to write out a flag if the log configuration was active the
whole process life or did change. I think nothing more complicated than
that is needed.

Kind regards, Thomas

>
> Thanks,
> Max
>
> Kind Regards, Thomas
>
>
>
>
> On Tue, Mar 29, 2016 at 9:00 PM, Max Ockner <max.ockner at oracle.com> wrote:
>
>> Hello,
>> Please review another Unified Logging change. They are almost done, and
>> we are serious this time.
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8151526
>> webrev: http://cr.openjdk.java.net/~mockner/8151526.01/
>>
>
> LogConfiguration::describe() takes the ConfigurationLock, which might be
> problematic for the error handler. I suppose the error handler could
> potentially deadlock if its thread already holds the lock. Unsure how to
> resolve this, because skipping to take the lock means that we might crash
> due to another thread changing the configuration as we read it.
>
> Thanks,
> Marcus
>
>
>> The logging configuration is now printed in each hs_err file. The output
>> is the same as you would see from -Xlog:logging=trace and it is obtained
>> from LogConfiguration::describe().
>>
>> Below is a sample of the hs_err contents. The Logging info is printed
>> after VM Arguments and Whitebox, and before Environment Variables.
>>
>> VM Arguments:
>> java_command: Kaboom
>> java_class_path (initial): .
>> Launcher Type: SUN_STANDARD
>>
>> Logging:
>> Available log levels: off, trace, debug, info, warning, error
>> Available log decorators: time (t), uptime (u), timemillis (tm),
>> uptimemillis (um), timenanos (tn), uptimenanos (un), hostname (hn), pid
>> (p), tid (ti), level (l), tags (tg)
>> Available log tags: alloc, age, barrier, biasedlocking, bot, census,
>> classhisto, classresolve, classinit, classload, classloaderdata,
>> classunload, classpath, compaction, cpu, cset, defaultmethods, ergo,
>> exceptions, exit, freelist, gc, heap, humongous, ihop, itables, jni,
>> liveness, logging, marking, metaspace, modules, monitorinflation, os,
>> phases, plab, promotion, preorder, protectiondomain, ref, refine, region,
>> remset, safepoint, safepointcleanup, scavenge, scrub, stacktrace, start,
>> startuptime, state, stats, stringdedup, stringtable, survivor, sweep, task,
>> thread, tlab, time, verboseverification, verify, vmoperation, vtables
>> Log output configuration:
>> #0: stdout all=off uptime,level,tags,
>> #1: stderr all=warning uptime,level,tags,
>>
>> Environment Variables:
>>
>> JAVA_HOME=/scratch/mockner/UL/8151526/build/linux-x86_64-normal-server-fastdebug/images/jdk
>>
>> PATH=/home/mockner/tools/webrev:/bin:/usr/bin:/usr/local/bin:/usr/sbin:/home/mockner/bin:/home/mockner/linux/bin
>> SHELL=/bin/bash
>> OS=Linux
>>
>>
>
>
>