RFR: 8224871: os::attempt_reserve_memory_at() tries too hard

[Erik Österlund]

Hi Per,

Thanks for the review.

/Erik

On 2019-06-04 10:02, Per Liden wrote:
> Looks good.
>
> /Per
>
> On 5/28/19 3:07 PM, Erik Österlund wrote:
>> Hi,
>>
>> The os::attempt_reserve_memory_at() function on BSD, linux and 
>> Solaris all try a bit too hard. They first try to mmap memory at a 
>> given address. If that failed, rather than giving up as expected, it 
>> tries in a loop to mmap random memory (without address hints), and 
>> looks if it so happens to be that it can from these completely random 
>> and arbitrary address ranges find overlapping ranges that happen to 
>> cross over the exact range that was requested, and then cuts out the 
>> excess and returns that. We really should just give up instead if the 
>> OS refused to hand out memory at the requested address.
>>
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8224871
>>
>> Webrev:
>> http://cr.openjdk.java.net/~eosterlund/8224871/webrev.00/
>>
>> Thanks,
>> /Erik