Unsafe vs MemorySegments / Bounds checking...

[Maurizio Cimadamore]

Glad to hear that JDK 24 helped. This particular fix has also been 
backported and will be in 23.0.2.

Maurizio

On 29/10/2024 21:18, Brian S O'Neill wrote:
> 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
>>>
>>
>