Making ENV Ractor-safe #4636
Making ENV Ractor-safe #4636
Conversation
|
Is there any performance impact for non-Ractor code? |
|
Also, does this mean you can use |
There is some performance impact, but the level of impact varies between methods. For some methods, it seems negligible. For others, there is a visible impact on speed, but for many of these the impact is comparatively insignificant when ENV is larger (because the overhead from the locks remains constant). |
Yes, it would be possible to have one Ractor store a value/message in ENV and have another Ractor read it. |
* --braces-after-func-def-line * --space-after-for
| static void | ||
| copy_env_pairs(const char **arr, int size) | ||
| { | ||
| char **env; | ||
| env = GET_ENVIRON(environ); | ||
| for (int i = 0; i < size; i++) { | ||
| const char *p = *env; | ||
| arr[i] = p; | ||
| env++; | ||
| } | ||
| FREE_ENVIRON(environ); | ||
| } |
There was a problem hiding this comment.
Copied entries may no longer be valid once other threads change any envs.
There was a problem hiding this comment.
More accurately, this function doesn't copy the env contents.
There was a problem hiding this comment.
Thank you for your time in reviewing this!
I agree that the function is not creating a deep copy of the environment contents. However, in my tests, simply copying the pointer to the original environment was enough. know that inconsistencies in the data are possible, but I believe that ENV already has inconsistent behavior when used in simultaneous threads. Is there a case I missed that causes an error in the program?
Thanks again!
There was a problem hiding this comment.
Therefore ENV isn't ractor-safe.
Before the ractor, GVL prevented it from the inconsistencies.
There was a problem hiding this comment.
Thank you. I will think about it some more.
It is important that the ENV object be accessible in Ractors. To make it Ractor-safe, its methods that get/set its values are now synchronized with this modification. This is done by placing a mutex around each of these methods. With this, the ENV object is now Ractor-safe and shareable. Additionally, tests are added to ensure that its behavior is correct in Ractors.