request for review (s) - 8005452: Create new flags for Metaspace resizing policy

[Jesper Wilhelmsson]

Jon,

OK, in that case I think the error message could be slightly more 
informative, just so that it is clear to someone that only sets one of 
them that the flag they set conflicts with the default value of another 
flag. How about this:

jio_fprintf(defaultStream::error_stream(),
             "MinMetaspaceFreeRatio (%s" UINTX_FORMAT ") must be less 
than or "
             "equal to MaxMetaspaceFreeRatio (%s" UINTX_FORMAT ")\n",
             FLAG_IS_DEFAULT(MinMetaspaceFreeRatio) ? "Default: " : "",
             MinMetaspaceFreeRatio,
             FLAG_IS_DEFAULT(MaxMetaspaceFreeRatio) ? "Default: " : "",
             MaxMetaspaceFreeRatio);

If you don't like this I'm fine with your current patch as well.
/Jesper


On 28/1/13 8:30 PM, Jon Masamitsu wrote:
> Jesper,
>
> If the user is increasing MinMetaspaceFreeRatio, and
> MaxMetaspaceFreeRatio is not compatible, maybe we
> should be forcing the user to think about MaxMetaspaceFreeRatio.
> It's not obvious to me that something like
>
> MaxMetaspaceFreeRatio = MinMetaspaceFreeRatio + 1
>
> is a good choice.
>
> Jon
>
> On 01/28/13 07:08, Jesper Wilhelmsson wrote:
>> On 2013-01-26 00:50, Jon Masamitsu wrote:
>>> I've update the webrev2 (now 2 separate webrevs)  for review comments.
>>>
>>> 8005452: NPG: Create new flags for Metaspace resizing policy
>>>
>>> http://cr.openjdk.java.net/~jmasa/8005452/webrev.03/
>>
>> I have looked at the flag changes and they look good. I have a
>> question though. How do we want to handle the case where the user sets
>> only MinMetaspaceFreeRatio = 30 ? With your current change this will
>> give an error because the min is larger than the default max (20).
>>
>> Would it make sense to assume that the user actually wants to use
>> min=30 and increase max to 30 as well? (or slightly more if they can't
>> be equal) And maybe issue a warning that the value of max has been
>> changed.
>> The error would then just be given if the user specifies both flags
>> and they don't work out.
>>
>> I'm not asking you to do this change now but it relates to other
>> changes we have done recently.
>> /Jesper
>>
>>
>>>
>>> 8006815: NPG: Trigger a GC for metadata collection just before the
>>> threshold
>>> is exceeded.
>>>
>>> http://cr.openjdk.java.net/~jmasa/8006815/webrev.01/
>>>
>>>
>>> On 1/16/2013 8:50 AM, Jon Masamitsu wrote:
>>>> I've added checks to arguments.cpp that are analogous to the
>>>> checks for MinHeapFreeRatio / MaxHeapFreeRatio
>>>>
>>>> Changes since webrev.00 are in arguments.cpp
>>>>
>>>> http://cr.openjdk.java.net/~jmasa/8005452/webrev.01/
>>>>
>>>> Thanks, Vitaly.
>>>>
>>>> Jon
>>>>
>>>> On 1/15/2013 5:55 AM, Vitaly Davidovich wrote:
>>>>> Hi Jon,
>>>>>
>>>>> Does it make sense to validate that the new flags are consistent
>>>>> (I.e. max
>>>>>> = min)? That is, if user changes one or both such that max<  min,
>>>>>> should
>>>>> VM report an error and not start?
>>>>>
>>>>> Thanks
>>>>>
>>>>> Sent from my phone
>>>>> On Jan 14, 2013 10:31 AM, "Jon Masamitsu"<jon.masamitsu at oracle.com>
>>>>> wrote:
>>>>>
>>>>>> 8005452: Create new flags for Metaspace resizing policy
>>>>>>
>>>>>> Previously the calculation of the metadata capacity at which
>>>>>> to do a GC (high water mark, HWM) to recover
>>>>>> unloaded classes used the MinHeapFreeRatio
>>>>>> and MaxHeapFreeRatio to decide on the next HWM.  That
>>>>>> generally left an excessive amount of unused capacity for
>>>>>> metadata.  This change adds specific flags for metadata
>>>>>> capacity with defaults more conservative in terms of
>>>>>> unused capacity.
>>>>>>
>>>>>> Added an additional check for doing a GC before expanding
>>>>>> the metadata capacity.  Required adding a new parameter to
>>>>>> get_new_chunk().
>>>>>>
>>>>>> Added some additional diagnostic prints.
>>>>>>
>>>>>> http://cr.openjdk.java.net/~**jmasa/8005452/webrev.00/<http://cr.openjdk.java.net/~jmasa/8005452/webrev.00/>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Thanks.
>>>>>>