Unsafe vs MemorySegments / Bounds checking...

[Brian S O'Neill]

With JDK 24, the overall performance regression drops down to 1.9%, 
which is similar to what I saw before JDK 23.

On 2024-10-29 12:20 PM, Brian S O'Neill wrote:
> I'll try the latest JDK 24 build and report back. One thing that 
> concerns me with the latest build is this error message when I enable 
> large pages (which helps with performance):
> 
> [0.027s][error][cds] Failed to commit static  region #3 (Heap)
> [0.027s][error][cds] Failed to read archived heap region into 
> 0x00000007ffe00000
> 
> 
> On 2024-10-29 12:07 PM, Maurizio Cimadamore wrote:
>>
>> On 29/10/2024 18:35, Brian S O'Neill wrote:
>>> If you recall, I did send you a reproducer, and you did verify the 
>>> regression. This is what led you to come up with a strategy to define 
>>> a derived VarHandle. This helped somewhat, but you observed the 
>>> inliner giving up when the code was embedded in a very large method. 
>>> JDK 23 appears to have introduced a regression that has made this worse. 
>>
>> The fact that you mention that 23 made it worse reminds me of [1], 
>> where a fix in 23 created an issue for adapted memory access var handles.
>>
>> If I recall correctly, the workaround we suggested was _also_ using 
>> adapted var handles.
>>
>> So I wonder if (a) you were already running into the issue in [1] and 
>> (b) because of that JDK 23 made it worse for you.
>>
>> Did you have a chance to try your project with the latest JDK 24 
>> build? Is the regression gone there? That would be useful to know 
>> regardless of the wider discussion.
>>
>> Maurizio
>>
>> [1] - https://mail.openjdk.org/pipermail/panama-dev/2024- 
>> September/020643.html
>>
>