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

[Christian Thalinger]

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?

> 
> 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