internals:zend_mm

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internals:zend_mm [2013/01/22 13:07]
krakjoe [Zend MM] just a bit more detail 		internals:zend_mm [2017/09/22 13:28] (current)
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 PHP is written entirely in C. In C, the programmer is responsible for the allocation and release of memory during runtime.  PHP is written entirely in C. In C, the programmer is responsible for the allocation and release of memory during runtime. 
  
-PHP has very specific requirements for management of memory and many modes of execution; all sharing the same set of requirements. +PHP has very specific requirements for management of memory and many modes of execution; all sharing a common set of requirements. 
  
 The memory manager in PHP, named Zend MM, facilitates these requirements in the same way, whatever the mode of execution, whatever the code. The memory manager in PHP, named Zend MM, facilitates these requirements in the same way, whatever the mode of execution, whatever the code.
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  large: when allocating large blocks of memory, it is important that the manager minimizes wastage.  large: when allocating large blocks of memory, it is important that the manager minimizes wastage.
  
-The MM provides the following (basic) functions:+The developer makes allocations that have two distinct life cycles: 
 +  
 + request: the most common type of allocation made; the developer requires the memory to service the current request 
 + 
 + persistent: the developer intends to reference the memory in multiple requests 
 + 
 +The MM provides the following (per request) functions:
  
  void*  emalloc(size_t size);  void*  emalloc(size_t size);
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  void   efree(void* pointer);  void   efree(void* pointer);
  
-They all share prototype and functionality with the standard C implementation, but the memory returned is optimized, and tracked. Tracking memory allows a margin of error not normally present in C programming: memory that is not free'd explicitly will normally be free'd by the implementation at the appropriate time, such as the end of the request, or the end of execution. +They all share prototype and functionality with the standard C implementation, but the allocation is optimized, and tracked. Tracking allocations allows a margin of error not normally present in C programming: memory that is not free'd explicitly will normally be free'd by the implementation at the appropriate time, such as the end of the request, or the end of execution.
- +
-The MM provides the following persistence functions:+
  
- void* pemalloc(size_t size); +Zend provides the following (persistence) functions:
- void* perealloc(void* pointer, size_t size); +
- void* pecalloc(size_t num, size_t count); +
- void  pefree(void* pointer);+
  
-Persistent memory is not managed, optimized, or tracked by the implementation, and should only be used if the developer requires a structure to survive requests.+ void* pemalloc(size_t size, zend_bool persistent); 
 + void* perealloc(void* pointer, size_t size, zend_bool persistent); 
 + void* pecalloc(size_t num, size_t count, zend_bool persistent); 
 + void  pefree(void* pointer, zend_bool persistent);
  
-The following diagrams and explanations provide insight into how and why Zend MM works the way it does.+Persistent memory is not optimized, or tracked by the implementation, and should only be used if the developer requires a structure to survive requests.
  
 +The following diagrams and explanations provide insight into how and why Zend MM manages the per request memory it allocates.
 ===== Struct zend_mm_heap ===== ===== Struct zend_mm_heap =====
 <code c> <code c>
internals/zend_mm.1358860052.txt.gz · Last modified: 2017/09/22 13:28 (external edit)

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