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

[Calvin Cheung]

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
>>
>