Slower Than C

[arshidkv12]

Hi
I tested with xdebug profile option with grind cache.
Functions are slower than c. How to speed up?

[ryangjchandler]

The difference in speed is likely due to converting between PHP types (Zval) and Rust types such as String, Vec, etc.

[joehoyle]

I think to test this assumption it could be a good idea to benchmark:

#[php_function]
fn should_be_fast(&Zval zval ) -> Zval {
    zval.shallow_clone()
}

I suspect we might actually have several inefficiencies in the calling bridging, unnecessarily allocating etc.

[ryangjchandler]

That would just be benchmarking a direct clone of a Zval though right? Not the Vec<T> allocations, etc?

[joehoyle]

I'm not sure, I think the #[php_function] may generate code that has additional allocations etc in.

[EdmondDantes]

The current approach is expected to introduce some performance overhead:

Calling a function from a wrapper function.
Copying variables to the stack.
In other words, if I create a function whose body does very little useful work and plan to call this function frequently, I will inevitably lose about 50% of performance.

I'm not sure how common this case is, but if necessary, it's possible to create a function without a wrapper and work directly with zend_execute_data* execute_data and zval* return_val.

[Xenira]

For calling functions more efficiently i use something like this: https://github.com/Xenira/php-iter-tools/blob/rust-impl/src/lib.rs#L1739

[arshidkv12]

I think zig is best for it https://github.com/arshidkv12/zig-php

[EdmondDantes]

@arshidkv12

export fn hello_world(execute_data: ?*php.zend_execute_data, return_value: ?*php.zval) void {
    _ = execute_data;
    _ = return_value;
    _ = php.php_printf("Hello from ZIG!\n");
}

@Xenira

That's exactly what I'm talking about – the same code can be written in Rust without any performance loss. We need to consider this implementation option.

[kakserpom]

@Xenira
Why don't we move your implementation from php-iter-tools into ext-php-rs?

[Xenira]

@kakserpom is on my todo list. Will create an issue for this.

[Xenira]

Probably want to create performance tests first though

[Xenira]

Speculations are probably correct. Lots of allocations and parsing going on.