RFR: 8317432: Async UL: Use memcpy instead of strcpy in Message ctr [v2]

[Johan Sjölen]

On Thu, 5 Oct 2023 10:24:54 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi,
>> 
>> This change does three things:
>> 
>> 1. At construction of message we used to compute `strlen` and then `strcpy`, we change this to do only one `strlen` and then a `memcpy` instead.
>> 2. A `strlen` used to be required to calculate the size when finding the next message in the iterator. We instead store the previously computed message length and so the `strlen` is no longer necessary. The cost of this is 8 bytes extra per message (64 -> 72 bytes).
>> 3. There's also some code which alters the alignment to explicitly handle the alignment of `Message` and ensure that `_pos` starts at a `Message`-aligned pointer.
>
> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Do not save the message length

Thank you for the reviews.

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PR Comment: https://git.openjdk.org/jdk/pull/16029#issuecomment-1761330498