RFR(S): JDK-8048150: Allow easy configurations for large CDS archives

[Karen Kinnear]

Ioi,

Could you piggyback on the PredictedLoadedClassCount existing flag? 
Yes, you would need special logic to decide a size based on the number of loaded classes in the archive. That
isn't terribly hard is it?
But I think this is temporary and so not adding a new flag could be a win.

I'm assuming that longer term, if we are copying the metadata for a dump (so as to add optimizations like locality
and interned strings and relocatability, etc.) then we could determine the appropriate
sizes we need at archive dump time? I will put that on the AppCDS phase 2 JEP as a wishlist item if that makes sense to you.

thanks,
Karen

On Jul 30, 2014, at 6:46 PM, Ioi Lam wrote:

> 
> On 7/30/14, 11:13 AM, Christian Thalinger wrote:
>> 
>> On Jul 30, 2014, at 10:41 AM, Ioi Lam <ioi.lam at oracle.com <mailto:ioi.lam at oracle.com>> wrote:
>> 
>>> 
>>> On 7/30/14, 9:31 AM, Christian Thalinger wrote:
>>>> On Jul 29, 2014, at 4:08 PM, Calvin Cheung <calvin.cheung at oracle.com <mailto:calvin.cheung at oracle.com>> wrote:
>>>> 
>>>>> In JDK8, if one wants to create a large CDS archive (with a lot of classes), one needs to add VM options like these
>>>>> 
>>>>> -XX:SharedReadWriteSize=200000000
>>>>> -XX:SharedReadOnlySize=200000000
>>>>> -XX:SharedMiscDataSize=22000000
>>>>> -XX:SharedMiscCodeSize=10000000
>>>>> 
>>>>> which is cumbersome and error-prone.
>>>>> 
>>>>> This change is to add the following 2 higher-level options to configure the sizes of the 4 regions (ro, rw, md, mc) of a shared archive.
>>>>> 
>>>>> -XX:+UseLargeSharedArchive (allow up to 300MB combined archive size)
>>>>> -XX:+UseHugeSharedArchive  (allow up to 800MB combined archive size)
>>>> Can we have only one new product flag instead of two?
>>> Christian,
>>> 
>>> Do you have any suggestion about what the single flag would look like?
>> 
>> Something like:  -XX:SharedArchiveSize={large,huge}
>> 
> (oops, I replied to the wrong Christian :-)
> 
> But that means we need to write a special parser for the SharedArchiveSize flag, and check for error cases, etc. I think it's better to reply on the built-in parser inside arguments.cpp.
> 
> - Ioi
> 
>>> 
>>> Thanks
>>> - Ioi
>>> 
>>>>> I tried a scenario with 19854 classes in the archive, the percentage of usage of the 4 regions are:
>>>>> ro (40%), rw (55%), md (3%), mc (2%)
>>>>> 
>>>>> ro space:  57948760 [ 40.6% of total] out of 134217728 bytes [43.2% used] at 0x0000000800000000
>>>>> rw space:  80259048 [ 56.2% of total] out of 134217728 bytes [59.8% used] at 0x0000000808000000
>>>>> md space:   4102376 [  2.9% of total] out of  23068672 bytes [17.8% used] at 0x0000000810000000
>>>>> mc space:    426525 [  0.3% of total] out of  23068672 bytes [ 1.8% used] at 0x0000000811600000
>>>>> total   : 142736709 [100.0% of total] out of 314572800 bytes [45.4% used]
>>>>> 
>>>>> The usage distribution also holds for a simpler scenario with 2467 classes.
>>>>> 
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8048150
>>>>> 
>>>>> webrev: http://cr.openjdk.java.net/~ccheung/8048150/webrev/ <http://cr.openjdk.java.net/%7Eccheung/8048150/webrev/>
>>>>> 
>>>>> Test:
>>>>>   JPRT
>>>>> 
>>>>> thanks,
>>>>> Calvin
>> 
>