path: root/include/mimalloc-types.h

/* ----------------------------------------------------------------------------
Copyright (c) 2018, Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"license.txt" at the root of this distribution.
-----------------------------------------------------------------------------*/
#pragma once
#ifndef __MIMALLOC_TYPES_H
#define __MIMALLOC_TYPES_H

#include <stdlib.h>   // size_t etc.
#include <stddef.h>   // ptrdiff_t
#include <stdint.h>   // uintptr_t, uint16_t, etc

// ------------------------------------------------------
// Variants
// ------------------------------------------------------

// Define NDEBUG in the release version to disable assertions.
// #define NDEBUG

// Define MI_STAT as 1 to maintain statistics; set it to 2 to have detailed statitistics (but costs some performance).
// #define MI_STAT 1

// Define MI_SECURE as 1 to encode free lists
// #define MI_SECURE 1

#if !defined(MI_SECURE) 
#define MI_SECURE 0
#endif

// Define MI_DEBUG as 1 for basic assert checks and statistics
// set it to 2 to do internal asserts,
// and to 3 to do extensive invariant checking.
#if !defined(MI_DEBUG)
#if !defined(NDEBUG) || defined(_DEBUG)
#define MI_DEBUG 1
#else
#define MI_DEBUG 0
#endif
#endif


// ------------------------------------------------------
// Platform specific values
// ------------------------------------------------------


// ------------------------------------------------------
// Size of a pointer.
// We assume that `sizeof(void*)==sizeof(intptr_t)`
// and it holds for all platforms we know of.
//
// However, the C standard only requires that:
//  p == (void*)((intptr_t)p))
// but we also need:
//  i == (intptr_t)((void*)i)
// or otherwise one might define an intptr_t type that is larger than a pointer...
// ------------------------------------------------------

#if INTPTR_MAX == 9223372036854775807LL
# define MI_INTPTR_SHIFT (3)
#elif INTPTR_MAX == 2147483647LL
# define MI_INTPTR_SHIFT (2)
#else
#error platform must be 32 or 64 bits
#endif

#define MI_INTPTR_SIZE  (1<<MI_INTPTR_SHIFT)


// ------------------------------------------------------
// Main internal data-structures
// ------------------------------------------------------

// Main tuning parameters for segment and page sizes
// Sizes for 64-bit, divide by two for 32-bit
#define MI_SMALL_PAGE_SHIFT               (13 + MI_INTPTR_SHIFT)      // 64kb
#define MI_LARGE_PAGE_SHIFT               ( 6 + MI_SMALL_PAGE_SHIFT)  // 4mb
#define MI_SEGMENT_SHIFT                  ( MI_LARGE_PAGE_SHIFT)      // 4mb

// Derived constants
#define MI_SEGMENT_SIZE                   (1<<MI_SEGMENT_SHIFT)
#define MI_SEGMENT_MASK                   ((uintptr_t)MI_SEGMENT_SIZE - 1)

#define MI_SMALL_PAGE_SIZE                (1<<MI_SMALL_PAGE_SHIFT)
#define MI_LARGE_PAGE_SIZE                (1<<MI_LARGE_PAGE_SHIFT)

#define MI_SMALL_PAGES_PER_SEGMENT        (MI_SEGMENT_SIZE/MI_SMALL_PAGE_SIZE)
#define MI_LARGE_PAGES_PER_SEGMENT        (MI_SEGMENT_SIZE/MI_LARGE_PAGE_SIZE)

#define MI_LARGE_SIZE_MAX                 (MI_LARGE_PAGE_SIZE/8)   // 512kb on 64-bit
#define MI_LARGE_WSIZE_MAX                (MI_LARGE_SIZE_MAX>>MI_INTPTR_SHIFT)


// Maximum number of size classes. (spaced exponentially in 16.7% increments)
#define MI_BIN_HUGE  (64U)

// Minimal alignment necessary. On most platforms 16 bytes are needed
// due to SSE registers for example. This must be at least `MI_INTPTR_SIZE`
#define MI_MAX_ALIGN_SIZE  16   // sizeof(max_align_t)

#if (MI_LARGE_WSIZE_MAX > 131072)
#error "define more bins"
#endif

typedef uintptr_t mi_encoded_t; 

// free lists contain blocks
typedef struct mi_block_s {
  mi_encoded_t next;  
} mi_block_t;


typedef enum mi_delayed_e {
  MI_NO_DELAYED_FREE = 0,
  MI_USE_DELAYED_FREE,
  MI_DELAYED_FREEING
} mi_delayed_t;


typedef union mi_page_flags_u {
  uint16_t value;
  struct {
    bool has_aligned;
    bool in_full;
  };
} mi_page_flags_t;

// Thread free list.
// We use 2 bits of the pointer for the `use_delayed_free` and `delayed_freeing` flags.
typedef union mi_thread_free_u {
  uintptr_t value;
  struct {
    mi_delayed_t delayed:2;
#if MI_INTPTR_SIZE==8
    uintptr_t head:62;    // head free block in the list (right-shifted by 2)
#elif MI_INTPTR_SIZE==4
    uintptr_t head:30;
#endif
  };
} mi_thread_free_t;

#define MI_TF_PTR_SHIFT (2)

// A page contains blocks of one specific size (`block_size`).
// Each page has three list of free blocks:
// `free` for blocks that can be allocated,
// `local_free` for freed blocks that are not yet available to `mi_malloc`
// `thread_free` for freed blocks by other threads
// The `local_free` and `thread_free` lists are migrated to the `free` list
// when it is exhausted. The separate `local_free` list is necessary to
// implement a monotonic heartbeat. The `thread_free` list is needed for
// avoiding atomic operations in the common case.
//
// `used - thread_freed` == actual blocks that are in use (alive)
// `used - thread_freed + |free| + |local_free| == capacity`
//
// note: we don't count `freed` (as |free|) instead of `used` to reduce
//       the number of memory accesses in the `mi_page_all_free` function(s).
// note: the funny layout here is due to:
// - access is optimized for `mi_free` and `mi_page_alloc`
// - using `uint16_t` does not seem to slow things down
typedef struct mi_page_s {
  // "owned" by the segment
  uint8_t               segment_idx;       // index in the segment `pages` array, `page == &segment->pages[page->segment_idx]`
  bool                  segment_in_use:1;  // `true` if the segment allocated this page
  bool                  is_reset:1;        // `true` if the page memory was reset

  // layout like this to optimize access in `mi_malloc` and `mi_free`
  mi_page_flags_t       flags;
  uint16_t              capacity;          // number of blocks committed
  uint16_t              reserved;          // numbes of blocks reserved in memory

  mi_block_t*           free;              // list of available free blocks (`malloc` allocates from this list)
  uintptr_t             cookie;            // random cookie to encode the free lists
  size_t                used;              // number of blocks in use (including blocks in `local_free` and `thread_free`)
  
  mi_block_t*           local_free;        // list of deferred free blocks by this thread (migrates to `free`)
  volatile uintptr_t    thread_freed;      // at least this number of blocks are in `thread_free`
  volatile mi_thread_free_t thread_free;   // list of deferred free blocks freed by other threads

  // less accessed info
  size_t                block_size;        // size available in each block (always `>0`)
  mi_heap_t*            heap;              // the owning heap
  struct mi_page_s*     next;              // next page owned by this thread with the same `block_size`
  struct mi_page_s*     prev;              // previous page owned by this thread with the same `block_size`

// improve page index calculation
#if MI_INTPTR_SIZE==8
  //void*                 padding[1];        // 10 words on 64-bit
#elif MI_INTPTR_SIZE==4
  void*                 padding[1];          // 12 words on 32-bit
#endif
} mi_page_t;



typedef enum mi_page_kind_e {
  MI_PAGE_SMALL,    // small blocks go into 64kb pages inside a segment
  MI_PAGE_LARGE,    // larger blocks go into a single page spanning a whole segment
  MI_PAGE_HUGE      // huge blocks (>512kb) are put into a single page in a segment of the exact size (but still 2mb aligned)
} mi_page_kind_t;

// Segments are large allocated memory blocks (2mb on 64 bit) from
// the OS. Inside segments we allocated fixed size _pages_ that
// contain blocks.
typedef struct mi_segment_s {
  struct mi_segment_s* next;
  struct mi_segment_s* prev;
  struct mi_segment_s* abandoned_next;
  size_t          abandoned;   // abandoned pages (i.e. the original owning thread stopped) (`abandoned <= used`)
  size_t          used;        // count of pages in use (`used <= capacity`)
  size_t          capacity;    // count of available pages (`#free + used`)
  size_t          segment_size;// for huge pages this may be different from `MI_SEGMENT_SIZE`
  size_t          segment_info_size;  // space we are using from the first page for segment meta-data and possible guard pages.
  uintptr_t       cookie;      // verify addresses in debug mode: `mi_ptr_cookie(segment) == segment->cookie`

  // layout like this to optimize access in `mi_free`
  size_t          page_shift;  // `1 << page_shift` == the page sizes == `page->block_size * page->reserved` (unless the first page, then `-segment_info_size`).
  uintptr_t       thread_id;   // unique id of the thread owning this segment
  mi_page_kind_t  page_kind;   // kind of pages: small, large, or huge
  mi_page_t       pages[1];    // up to `MI_SMALL_PAGES_PER_SEGMENT` pages
} mi_segment_t;


// ------------------------------------------------------
// Heaps
// Provide first-class heaps to allocate from.
// A heap just owns a set of pages for allocation and
// can only be allocate/reallocate from the thread that created it.
// Freeing blocks can be done from any thread though.
// Per thread, the segments are shared among its heaps.
// Per thread, there is always a default heap that is
// used for allocation; it is initialized to statically
// point to an empty heap to avoid initialization checks
// in the fast path.
// ------------------------------------------------------

// Thread local data
typedef struct mi_tld_s mi_tld_t;

// Pages of a certain block size are held in a queue.
typedef struct mi_page_queue_s {
  mi_page_t* first;
  mi_page_t* last;
  size_t     block_size;
} mi_page_queue_t;

#define MI_BIN_FULL  (MI_BIN_HUGE+1)

// A heap owns a set of pages.
struct mi_heap_s {
  mi_tld_t*             tld;
  mi_page_t*            pages_free_direct[MI_SMALL_WSIZE_MAX + 2];   // optimize: array where every entry points a page with possibly free blocks in the corresponding queue for that size.
  mi_page_queue_t       pages[MI_BIN_FULL + 1];                      // queue of pages for each size class (or "bin")
  volatile mi_block_t*  thread_delayed_free;
  uintptr_t             thread_id;                                   // thread this heap belongs too
  uintptr_t             cookie;
  uintptr_t             random;                                      // random number used for secure allocation
  size_t                page_count;                                  // total number of pages in the `pages` queues.
  bool                  no_reclaim;                                  // `true` if this heap should not reclaim abandoned pages
};



// ------------------------------------------------------
// Debug
// ------------------------------------------------------

#define MI_DEBUG_UNINIT     (0xD0)
#define MI_DEBUG_FREED      (0xDF)


#if (MI_DEBUG)
// use our own assertion to print without memory allocation
void _mi_assert_fail(const char* assertion, const char* fname, unsigned int line, const char* func );
#define mi_assert(expr)     ((expr) ? (void)0 : _mi_assert_fail(#expr,__FILE__,__LINE__,__func__))
#else
#define mi_assert(x)
#endif

#if (MI_DEBUG>1)
#define mi_assert_internal    mi_assert
#else
#define mi_assert_internal(x)
#endif

#if (MI_DEBUG>2)
#define mi_assert_expensive   mi_assert
#else
#define mi_assert_expensive(x)
#endif

// ------------------------------------------------------
// Statistics
// ------------------------------------------------------

#ifndef MI_STAT
#if (MI_DEBUG>0)
#define MI_STAT 2
#else
#define MI_STAT 0
#endif
#endif

typedef struct mi_stat_count_s {
  int64_t allocated;
  int64_t freed;
  int64_t peak;
  int64_t current;
} mi_stat_count_t;

typedef struct mi_stat_counter_s {
  int64_t total;
  int64_t count;
} mi_stat_counter_t;

typedef struct mi_stats_s {
  mi_stat_count_t segments;
  mi_stat_count_t pages;
  mi_stat_count_t reserved;
  mi_stat_count_t committed;
  mi_stat_count_t reset;
  mi_stat_count_t segments_abandoned;
  mi_stat_count_t pages_abandoned;
  mi_stat_count_t pages_extended;
  mi_stat_count_t mmap_calls;
  mi_stat_count_t mmap_right_align;
  mi_stat_count_t mmap_ensure_aligned;
  mi_stat_count_t threads;
  mi_stat_count_t huge;
  mi_stat_count_t malloc;
  mi_stat_counter_t searches;
#if MI_STAT>1
  mi_stat_count_t normal[MI_BIN_HUGE+1];
#endif
} mi_stats_t;


void _mi_stat_increase(mi_stat_count_t* stat, size_t amount);
void _mi_stat_decrease(mi_stat_count_t* stat, size_t amount);
void _mi_stat_counter_increase(mi_stat_counter_t* stat, size_t amount);

#if (MI_STAT)
#define mi_stat_increase(stat,amount)         _mi_stat_increase( &(stat), amount)
#define mi_stat_decrease(stat,amount)         _mi_stat_decrease( &(stat), amount)
#define mi_stat_counter_increase(stat,amount) _mi_stat_counter_increase( &(stat), amount)
#else
#define mi_stat_increase(stat,amount)         (void)0
#define mi_stat_decrease(stat,amount)         (void)0
#define mi_stat_counter_increase(stat,amount) (void)0
#endif

#define mi_heap_stat_increase(heap,stat,amount)  mi_stat_increase( (heap)->tld->stats.stat, amount)
#define mi_heap_stat_decrease(heap,stat,amount)  mi_stat_decrease( (heap)->tld->stats.stat, amount)


// ------------------------------------------------------
// Thread Local data
// ------------------------------------------------------

// Queue of segments
typedef struct mi_segment_queue_s {
  mi_segment_t* first;
  mi_segment_t* last;
} mi_segment_queue_t;


// Segments thread local data
typedef struct mi_segments_tld_s {
  mi_segment_queue_t  small_free;   // queue of segments with free small pages
  size_t              count;        // current number of segments
  size_t              peak;         // peak number of segments
  size_t              cache_count;  // number of segments in the cache
  mi_segment_t*       cache;        // small cache of segments (to avoid repeated mmap calls)
  mi_stats_t*         stats;        // points to tld stats
} mi_segments_tld_t;

// OS thread local data
typedef struct mi_os_tld_s {
  uintptr_t           mmap_next_probable;  // probable next address start allocated by mmap (to guess which path to take on alignment)
  void*               mmap_previous;       // previous address returned by mmap
  uint8_t*            pool;                // pool of segments to reduce mmap calls on some platforms
  size_t              pool_available;      // bytes available in the pool
  mi_stats_t*         stats;               // points to tld stats
} mi_os_tld_t;

// Thread local data
struct mi_tld_s {
  unsigned long long  heartbeat;     // monotonic heartbeat count
  mi_heap_t*          heap_backing;  // backing heap of this thread (cannot be deleted)
  mi_segments_tld_t   segments;      // segment tld 
  mi_os_tld_t         os;            // os tld
  mi_stats_t          stats;         // statistics
};

#endif