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

[Christian Thalinger]

On Jul 30, 2014, at 10:41 AM, Ioi Lam <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> 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}

> 
> 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/
>>> 
>>> Test:
>>>    JPRT
>>> 
>>> thanks,
>>> Calvin