RFR(S) 8233093: Move CDS heap oopmaps into new MetaspaceShared::bm region

[Ioi Lam]

Look good!

Thanks
- Ioi

On 3/25/20 1:56 PM, Calvin Cheung wrote:
> Hi Ioi,
>
> Thanks for your review.
>
> On 3/25/20 11:26 AM, Ioi Lam wrote:
>> Hi Calvin,
>>
>> Looks good. Just some minor nits for filemap.cpp:
>>
>> 1244   if (closed_oopmaps != NULL && open_oopmaps != NULL) {
>> 1245     size_t curr_offset = write_oopmaps(closed_oopmaps, 
>> ptrmap->size_in_bytes(), buffer);
>> 1246     curr_offset = write_oopmaps(open_oopmaps, curr_offset, buffer);
>>
>> There's no need to write to curr_offset on line 1246.
>>
> Fixed.
>> ----
>>
>> Unnecessary new line at 1897.
>>
> Removed.
>> ----
>>
>> 1599     current_info()->unmap_region(MetaspaceShared::bm);
>>
>> This call can be removed, because the "bm" region will be eventually 
>> unmapped by the new code in 
>> MetaspaceShared::initialize_shared_spaces(). This way, if we later 
>> need to relocate the archived heap relocation, there's no need to map 
>> the "bm" region again.
>
> I've replaced it with a comment.
>
> updated webrev:
>
>     http://cr.openjdk.java.net/~ccheung/jdk15/8233093/webrev.01/
>
> thanks,
>
> Calvin
>
>>
>> Thanks
>> - Ioi
>>
>>
>> On 3/25/20 9:39 AM, Calvin Cheung wrote:
>>> RFE: https://bugs.openjdk.java.net/browse/JDK-8233093
>>>
>>> webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8233093/webrev.00/
>>>
>>> The MetaspaceShared::bm region was introduced via JDK-8231610 
>>> (Relocate the CDS archive if it cannot be mapped to the requested 
>>> address) and only used during archive loading. The region will be 
>>> unmapped afterwards to save memory footprint. Since the heap oopmaps 
>>> are also only used during archive loading, it makes sense for them 
>>> to reside in the "bm" region as well.
>>>
>>> Before:
>>> [0.753s][debug][cds] ro space: 7552120 [ 59.7% of total] out of 
>>> 7553024 bytes [100.0% used] at 0x00000008003e1000
>>> [0.753s][debug][cds] bm space: 184320 [ 1.5% of total] out of 184320 
>>> bytes [100.0% used] at 0x0000000000000000
>>>
>>> After:
>>> [0.766s][debug][cds] ro space: 7525856 [ 59.5% of total] out of 
>>> 7528448 bytes [100.0% used] at 0x00000008003e1000
>>> [0.766s][debug][cds] bm space: 208896 [ 1.7% of total] out of 208896 
>>> bytes [100.0% used] at 0x0000000000000000
>>>
>>> Passed tiers 1 - 4 testing.
>>>
>>> thanks,
>>>
>>> Calvin
>>>
>>