RFR(xxxs): 8204164: OOM-only logging in Metaspace

[David Holmes]

Hi Kirk,

Please note I was simply commenting on the proposal to remove a tag from 
unified logging - something which will result in a failure to start the 
VM for anyone currently using that tag.

Cheers,
David

On 2/06/2018 5:39 AM, Kirk Pepperdine wrote:
> Hi David,
> 
> As you likely know, I’ve bee dealing with changes in GC logging for what feels like forever…. And I support parsing GC logs as far back as the 1.4.2. Bottom line, logs need to change to reflect changes in the implementation…  IME, changes in logs come in two forms, those that add materially to the log and those that are just arbitrary in nature and don’t add any real value. Sometimes even correcting a “not so accurate representation” isn’t enough to actually justify the change. However, when there is real benefits there is no question, the change should be made and I’ll happily adjust my tooling to accommodate. Frustration sets in when the changes are arbitary in that they offer no material change to the information in the logs. This serves only to complicate the parsing of the file. As an example, over the years there have been more than 10 changes in the format to how remark cycles in CMS have been reported yet the information in each of these changes is pretty much the same.
> 
> In this case the oom tag may add context that will prove to be useful. As tags are optional in the log, I don’t rely on them but I do use them to add context.
> 
> Kind regards,
> Kirk
> 
>   1, 2018, at 1:22 AM, David Holmes <david.holmes at oracle.com> wrote:
>>
>> On 1/06/2018 6:37 AM, coleen.phillimore at oracle.com wrote:
>>> I agree, this seems good, and fine with me to remove freelist.
>>
>> Have we established any policy for lifecycle management of logging tags? If you just rip out a tag and someone has a special logging script they run occasionally if they need to gather specific information, then they suddenly get a failure because someone decided "naw don't need that tag".
>>
>> David
>> -----
>>
>>> Coleen
>>> On 5/31/18 3:35 PM, Gerard Ziemski wrote:
>>>> hi Thomas,
>>>>
>>>> Your enhancement looks useful to me.
>>>>
>>>> Removing “freelist” tag from “metaspace” seems worthy of a separate issue/discussion.
>>>>
>>>>
>>>> cheers
>>>>
>>>>> On May 31, 2018, at 6:36 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> very tiny improvement. The intent is to be able to restrict metaspace
>>>>> logging to OOM situations.
>>>>>
>>>>> CR: OOM-only logging in Metaspace
>>>>> Webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8204164-oom-only-logging-in-metaspace/webrev.00/webrev/
>>>>>
>>>>> -- 
>>>>>
>>>>> On a related note, would anyone be offended if I were to remove the
>>>>> "freelist" logging tag from the metaspace coding? I am not sure that
>>>>> is useful in any way.
>>>>>
>>>>> Thanks, Thomas
>