Request for review (S): 7166894 Add gc cause to Full GC logging for all collectors
mikael.vidstedt at oracle.com
Fri May 11 10:17:16 PDT 2012
I'm all for improving the information in the log messages, great work!
However, I'm not sure I'm warm and fuzzy about potentially breaking
users' log parsers in a minor update. My preference would be to have the
PrintGCCause flag be default false in jdk7 and default true in jdk8+. In
general I'd prefer to only change the log messages in major releases.
On 2012-05-11 07:30, Bengt Rutisson wrote:
> Hi Kris,
> Thanks again for looking at this.
> I had to make some minor changes make it compile on all platforms.
> Mostly some explicit casts to const char*. Here is an updated webrev:
> More comments inline.
> On 2012-05-08 16:43, Krystal Mok wrote:
>> Hi Bengt,
>> The current factoring looks nice and uniform. Thanks :-)
>> But for most minor GCs and both CMS pause phases, the extra logging
>> doesn't really give additional information.
>> Most minor GCs are going to say "Allocation Failure", and the two CMS
>> phases would change from, e.g.
>> [GC [1 CMS-initial-mark
>> to something like
>> [GC (CMS Initial Mark) [1 CMS-initial-mark
>> which is probably reasonable given the scope of the change, but not
>> really helpful.
>> The "real cause", such as which generation (or perhaps System.gc()
>> with ExplicitGCInvokesConcurrent, or even GC locker) is triggering
>> this collection cycle, may be more useful, but it's hard to fit into
>> the current form.
> Yes, I think you are correct in both cases. The gc cause that we have
> available does not always add a lot of information. This is relevant
> to fix but it is a slightly different issue than what this patch sets
> out to fix. Let's try to get this in first and then evaluate how the
> GC causes should be set.
>> - Kris
>> On Tue, May 8, 2012 at 10:18 PM, Bengt Rutisson
>> <bengt.rutisson at oracle.com <mailto:bengt.rutisson at oracle.com>> wrote:
>> Hi again everyone,
>> It seems like the feedback on hotspot-gc-use is that we should
>> add the GC cause to all collectors but also provide a switch to
>> turn this logging off.
>> Here is an updated webrev:
>> * GC cause logged for all collectors
>> * Added the flag -XX:-PrintGCCause to turn the new information off
>> * Refactored the string concatenation code into a helper class
>> I guess I will also have to update the CR to now reflect the fact
>> that this does not just concern full GCs anymore.
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