RFR: 8065331: Add JVM trace events for failed allocations

Erik Helin erik.helin at oracle.com
Wed Apr 8 16:09:02 UTC 2015


On 2015-04-08, Marcus Larsson wrote:
> On 04/08/2015 05:13 PM, Erik Helin wrote:
> >On 2015-04-08, Marcus Larsson wrote:
> >>Hi again,
> >>
> >>During offline discussions with Erik Helin we decided to skip the gc-attempt
> >>counter altogether, since this information had little value. Also, as the
> >>"Collect for allocation" event would always be accompanied by the (already
> >>existing) garbage collection events, this event is unnecessary and has been
> >>removed as well. Instead, to see allocations pending a particular GC, one
> >>can look at "Allocations requiring GC" events preceding the garbage
> >>collection event sent for that GC.
> >>
> >>New (significantly smaller) webrev:
> >>http://cr.openjdk.java.net/~mlarsson/8065331/webrev.02/
> >Looks good to me, Reviewed.
> >
> >Thanks,
> >Erik
> 
> Thank you Erik!

Just had a quick look at the patch file and found this:

@@ -210,7 +210,7 @@
 class VM_CollectForMetadataAllocation: public VM_GC_Operation {
  private:
   MetaWord*                _result;
-  size_t                   _size;     // size of object to be allocated
+  size_t                   _size;        // size of object to be allocated

Why did you change the indentation of the comment?

Thanks,
Erik

> Marcus
> 
> >>Thanks,
> >>Marcus
> >>
> >>
> >>On 04/02/2015 02:55 AM, Marcus Larsson wrote:
> >>>Hi Jon,
> >>>
> >>>Thank you for looking at this.
> >>>
> >>>The way I intended the gc count information to be useful is to indicate if/when allocations keep failing. Problematic allocations would then have a gc count higher than 1. It's not really critical that this is the exact total, as it's just an indication, so a partial GC count could work I guess. If you think it would be better I can take a look at how I can reduce the CR by being less precise with this counter.
> >>>
> >>>Thanks,
> >>>Marcus
> >>>
> >>>----- Original Message -----
> >>>From: jon.masamitsu at oracle.com
> >>>To: hotspot-gc-dev at openjdk.java.net
> >>>Sent: Wednesday, 1 April, 2015 4:44:30 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> >>>Subject: Re: RFR: 8065331: Add JVM trace events for failed allocations
> >>>
> >>>Marcus,
> >>>
> >>>These changes are rather extensive and the CR is rather thin
> >>>on details.  How will the GC count information be useful?
> >>>Is it critical that it be the total GC count for failed allocation?
> >>>Could some partial GC count that does not require such
> >>>extensive changes be almost as useful?
> >>>
> >>>Thanks.
> >>>
> >>>Jon
> >>>
> >>>On 3/30/2015 3:54 PM, Marcus Larsson wrote:
> >>>>Ping!
> >>>>
> >>>>----- Original Message -----
> >>>>From: marcus.larsson at oracle.com
> >>>>To: hotspot-gc-dev at openjdk.java.net
> >>>>Sent: Tuesday, 24 March, 2015 7:35:08 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> >>>>Subject: RFR: 8065331: Add JVM trace events for failed allocations
> >>>>
> >>>>Hi,
> >>>>
> >>>>Please review the following patch adding new trace events for allocations requiring GC, and GCs triggered by allocation. See the JEP for a description of these two new events.
> >>>>
> >>>>CR:
> >>>>https://bugs.openjdk.java.net/browse/JDK-8065331
> >>>>
> >>>>Webrev:
> >>>>http://cr.openjdk.java.net/~mlarsson/8065331/webrev.00/
> >>>>
> >>>>JEP:
> >>>>https://bugs.openjdk.java.net/browse/JDK-8060092
> >>>>
> >>>>Tests:
> >>>>jprt, jtreg
> >>>>
> >>>>Thanks,
> >>>>Marcus
> 


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