rfc:fiber

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rfc:fiber [2018/04/17 23:52]
lvht
rfc:fiber [2018/06/12 07:40]
krakjoe move back to discussion
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 === Implementation Detail === === Implementation Detail ===
-In our simple implementation, we only backup/restore the **zend stack**. If you pause a Fiber in some internal function call like `array_map`, the c stack frame maybe over write which will trigger coredump. +In our simple implementation, we only backup/restore the **zend stack**. We **cannot** pause a Fiber during internal function call like `array_map`.
- +
-Martin Schröder has another implementation at https://github.com/fiberphp/fiber-ext/pull/30. Martin's work backup/restore both the zend stack and the c stack. +
- +
- +
-^Property^Martin's Fiber^Our Fiber^ +
-|Minimum Memory Usage|VM stack only (4 KB)|VM & C stack (4 KB + 4 KB)| +
-|Supported Architecturs|any platform supported by compiler|only x86 systems at this time| +
-|Yield in Internal Function|unsupported|supported| +
-|Yield in Iterator|unsupported|supported|+
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
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 ===== Open Issues ===== ===== Open Issues =====
-<blockquote>What happens if there are internal calls on the call stack?Say something like array_map(function() { await; }, [1, 2, 3]); inside a fiber.  +<blockquote>Why not support backup/restore the stack?</blockquote> 
-</blockquote>+Martin Schröder is working on this at https://github.com/fiberphp/fiber-ext/pull/30. 
  
-Calling Fiber::yield in a internal call will trigger a fatal error.+And here is the comparison. 
 +^Property^Stackless Fiber^Native Fiber^ 
 +|1 Minimum Memory Usage|VM stack only (4 KB)|VM & C stack (4 KB + 4 KB)| 
 +|2 Supported Architecturs|any platform|x86 at this time| 
 +|3 Yield in Internal Function|unsupported|supported| 
 +|4 Yield in Iterator|unsupported|supported|
  
-<blockquote>How do you determine when a fiber has returned? Separate methods similar to Generator would be better.</blockquote>+Stackless fiber use less memory and are not platform-dependend (1 & 2) which makes them very portable and efficient. They do however lack support for anything that involves internal function calls (3) including opcode handlers (4, e.g. foreach loop).
  
-Offering methods like **Fiber::alive()**,**Fiber::running()** makes any meaningful difference to check the return value of Fiber::status(). It is just a coding style issue.+Native fibers are very platform-dependend (2and use more memory because they do need to allocate a C call stack (1). While memory allocation will be done using mmap() it will still reserve virtual memory (can be problematic for a large number of fibers on 32 bit systems due to limited virtual memory addressing). The big advantage is that all kinds of internal function call (3 & 4) are supported without any changes to the existing codebase.
  
-And as a language feature, Fiber should only offer the essential API and let other works to the userland code.+<blockquote>Why not introduce helper like **Fiber::alive(),Fiber::running()**?</blockquote>
  
-<blockquote>Using Fiber::resume() to initialize the fiber and resume feels awkward. Separate methods again would be better.</blockquote>+And as a language feature, Fiber should only offer the essential API. User can implement these methods in user land code easily. 
 + 
 +<blockquote>Why not introduce a dedicate method other than **Fiber::resume()** for Fiber initialization?</blockquote>
  
 Both Ruby's Fiber and Lua's coroutine using the same **resume()** API to **init** and **resume** their coroutine. Both Ruby's Fiber and Lua's coroutine using the same **resume()** API to **init** and **resume** their coroutine.
- 
-<blockquote>I think a keyword here would be beneficial, even if it has a minor BC impact.</blockquote> 
- 
-Introducing new keywords does not offer any essential benefit but only cause BC impact. 
- 
-Both Ruby's Fiber and Lua's coroutine use method to pause and resume their coroutine. 
  
 ===== Unaffected PHP Functionality ===== ===== Unaffected PHP Functionality =====
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 ===== Future Scope ===== ===== Future Scope =====
-This sections details areas where the feature might be improved in future, but that are not currently proposed in this RFC. 
  
-===== Proposed Voting Choices ===== +Syntax like async/await can be implemented in the future, but it's out of the scope of this RFC.
-2/3+1 voting majority+
  
 ===== Patches and Tests ===== ===== Patches and Tests =====
rfc/fiber.txt · Last modified: 2018/06/12 07:40 by krakjoe