perf - removes pinning

[AlliBalliBaba]

I noticed that it's not necessary to pin a string if it's being used explicitly during a CGO function call (see also this discussion in the google forums.

zend_string_init will always copy the underlying string anyways so removing pinning for most globals is safe.

In the flamegraphs you can see that Pinner.Pin and Pinner.Unpin currently consume around 7% of the CPU profile for the optimized 'Hello World'. Without Pinning most of that time is gone.

With Pinner

Without Pinner

The only way to optimize this even more would be by directly using the allocated go string as a zend_string (not sure if this is currently possible)

[dunglas]

Good idea

[withinboredom]

NICE!

The only way to optimize this even more would be by directly using the allocated go string as a zend_string (not sure if this is currently possible)

That would require pinning. From the thread you linked to:

Unless, the C function stores the pointer and it's kept after the call returns, correct? That's what I mean by calling the function keep_this_pointer in the second example. In this case, it would be necessary, I'm assuming?

Ah, yes, in that case the pointer does have to be pinned.

[AlliBalliBaba]

That would require pinning. From the thread you linked to:

I guess you're right. So maybe this is the most efficient way to pass a string to PHP currently. I know that CGO calls themselves have some overhead because of entersyscall and exitsyscall. But that overhead seems to be smaller than that from pinning.