[Rev 01] RFR: Add a limition to allocate object heap in aarch64 with tsan enabled.

[Jie He]

On Fri, 24 Apr 2020 05:37:10 GMT, Jie He <github.com+10233373+jhe33 at openjdk.org> wrote:

>> src/hotspot/os/posix/os_posix.cpp line 550:
>> 
>>> 549:   u8 vm_addr_u8 = reinterpret_cast<u8>(&__FUNCTION__);
>>> 550:   // High address in 48bits user space is like 0x0000ffffxxxxxxxx.
>>> 551:   assert((vm_addr_u8  >> msb_in_aarch64) == 0x1, "warning: allocation could fail in non 48-bit address space.");
>> 
>> Is this based on kHiAppMemBeg = 0x0ffff00000000ull and kHiAppMemEnd = 0x1000000000000ull?
>> Mentioning these two constants like kMidAppMemBeg and kMidAppMemEnd above would be a more helpful comment.
>
> dynamic libraries will be loaded between kHiAppMemBeg and kHiAppMemEnd . it makes hard to allocate large continuous
> space.

oh, I see what you mean.

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PR: https://git.openjdk.java.net/tsan/pull/6