RFR(S): 8014408: G1: crashes with assert assert(prev_committed_card_num == _committed_max_card_num) failed

[John Cuthbertson]

Hi Everyone,

Can I have a couple of reviews of the fix for this assertion failure? 
The webrev can be found at: 
http://cr.openjdk.java.net/~johnc/8014408/webrev.0/

Summary:
This was an assertion I recently added and is used as a consistency 
check for the size of the card counts table. The problem was that there 
was a mismatch between the setting of _committed_card_num and 
prev_committed_card_num. An upper bound was used when setting the former 
and this was missing when calculating the latter. It only showed up on a 
system where the allocation alignment was 64k. I moved the calculation 
of the number of cards for a given committed table size into a helper 
routine and use the helper routine to set these values.

Testing:
The failing test cases on the system they fail on; spec jvm98 with MTT=0

Thanks,

JohnC