From 7bb481fda9ecb134804b49c2ce77ca28f7eea583 Mon Sep 17 00:00:00 2001 From: Hans-Christoph Steiner Date: Fri, 30 Mar 2012 20:42:12 -0400 Subject: Imported Upstream version 2.0.3 --- src/mem3.c | 687 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 687 insertions(+) create mode 100644 src/mem3.c (limited to 'src/mem3.c') diff --git a/src/mem3.c b/src/mem3.c new file mode 100644 index 0000000..1a1b791 --- /dev/null +++ b/src/mem3.c @@ -0,0 +1,687 @@ +/* +** 2007 October 14 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This file contains the C functions that implement a memory +** allocation subsystem for use by SQLite. +** +** This version of the memory allocation subsystem omits all +** use of malloc(). The SQLite user supplies a block of memory +** before calling sqlite3_initialize() from which allocations +** are made and returned by the xMalloc() and xRealloc() +** implementations. Once sqlite3_initialize() has been called, +** the amount of memory available to SQLite is fixed and cannot +** be changed. +** +** This version of the memory allocation subsystem is included +** in the build only if SQLITE_ENABLE_MEMSYS3 is defined. +*/ +#include "sqliteInt.h" + +/* +** This version of the memory allocator is only built into the library +** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not +** mean that the library will use a memory-pool by default, just that +** it is available. The mempool allocator is activated by calling +** sqlite3_config(). +*/ +#ifdef SQLITE_ENABLE_MEMSYS3 + +/* +** Maximum size (in Mem3Blocks) of a "small" chunk. +*/ +#define MX_SMALL 10 + + +/* +** Number of freelist hash slots +*/ +#define N_HASH 61 + +/* +** A memory allocation (also called a "chunk") consists of two or +** more blocks where each block is 8 bytes. The first 8 bytes are +** a header that is not returned to the user. +** +** A chunk is two or more blocks that is either checked out or +** free. The first block has format u.hdr. u.hdr.size4x is 4 times the +** size of the allocation in blocks if the allocation is free. +** The u.hdr.size4x&1 bit is true if the chunk is checked out and +** false if the chunk is on the freelist. The u.hdr.size4x&2 bit +** is true if the previous chunk is checked out and false if the +** previous chunk is free. The u.hdr.prevSize field is the size of +** the previous chunk in blocks if the previous chunk is on the +** freelist. If the previous chunk is checked out, then +** u.hdr.prevSize can be part of the data for that chunk and should +** not be read or written. +** +** We often identify a chunk by its index in mem3.aPool[]. When +** this is done, the chunk index refers to the second block of +** the chunk. In this way, the first chunk has an index of 1. +** A chunk index of 0 means "no such chunk" and is the equivalent +** of a NULL pointer. +** +** The second block of free chunks is of the form u.list. The +** two fields form a double-linked list of chunks of related sizes. +** Pointers to the head of the list are stored in mem3.aiSmall[] +** for smaller chunks and mem3.aiHash[] for larger chunks. +** +** The second block of a chunk is user data if the chunk is checked +** out. If a chunk is checked out, the user data may extend into +** the u.hdr.prevSize value of the following chunk. +*/ +typedef struct Mem3Block Mem3Block; +struct Mem3Block { + union { + struct { + u32 prevSize; /* Size of previous chunk in Mem3Block elements */ + u32 size4x; /* 4x the size of current chunk in Mem3Block elements */ + } hdr; + struct { + u32 next; /* Index in mem3.aPool[] of next free chunk */ + u32 prev; /* Index in mem3.aPool[] of previous free chunk */ + } list; + } u; +}; + +/* +** All of the static variables used by this module are collected +** into a single structure named "mem3". This is to keep the +** static variables organized and to reduce namespace pollution +** when this module is combined with other in the amalgamation. +*/ +static SQLITE_WSD struct Mem3Global { + /* + ** Memory available for allocation. nPool is the size of the array + ** (in Mem3Blocks) pointed to by aPool less 2. + */ + u32 nPool; + Mem3Block *aPool; + + /* + ** True if we are evaluating an out-of-memory callback. + */ + int alarmBusy; + + /* + ** Mutex to control access to the memory allocation subsystem. + */ + sqlite3_mutex *mutex; + + /* + ** The minimum amount of free space that we have seen. + */ + u32 mnMaster; + + /* + ** iMaster is the index of the master chunk. Most new allocations + ** occur off of this chunk. szMaster is the size (in Mem3Blocks) + ** of the current master. iMaster is 0 if there is not master chunk. + ** The master chunk is not in either the aiHash[] or aiSmall[]. + */ + u32 iMaster; + u32 szMaster; + + /* + ** Array of lists of free blocks according to the block size + ** for smaller chunks, or a hash on the block size for larger + ** chunks. + */ + u32 aiSmall[MX_SMALL-1]; /* For sizes 2 through MX_SMALL, inclusive */ + u32 aiHash[N_HASH]; /* For sizes MX_SMALL+1 and larger */ +} mem3 = { 97535575 }; + +#define mem3 GLOBAL(struct Mem3Global, mem3) + +/* +** Unlink the chunk at mem3.aPool[i] from list it is currently +** on. *pRoot is the list that i is a member of. +*/ +static void memsys3UnlinkFromList(u32 i, u32 *pRoot){ + u32 next = mem3.aPool[i].u.list.next; + u32 prev = mem3.aPool[i].u.list.prev; + assert( sqlite3_mutex_held(mem3.mutex) ); + if( prev==0 ){ + *pRoot = next; + }else{ + mem3.aPool[prev].u.list.next = next; + } + if( next ){ + mem3.aPool[next].u.list.prev = prev; + } + mem3.aPool[i].u.list.next = 0; + mem3.aPool[i].u.list.prev = 0; +} + +/* +** Unlink the chunk at index i from +** whatever list is currently a member of. +*/ +static void memsys3Unlink(u32 i){ + u32 size, hash; + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 ); + assert( i>=1 ); + size = mem3.aPool[i-1].u.hdr.size4x/4; + assert( size==mem3.aPool[i+size-1].u.hdr.prevSize ); + assert( size>=2 ); + if( size <= MX_SMALL ){ + memsys3UnlinkFromList(i, &mem3.aiSmall[size-2]); + }else{ + hash = size % N_HASH; + memsys3UnlinkFromList(i, &mem3.aiHash[hash]); + } +} + +/* +** Link the chunk at mem3.aPool[i] so that is on the list rooted +** at *pRoot. +*/ +static void memsys3LinkIntoList(u32 i, u32 *pRoot){ + assert( sqlite3_mutex_held(mem3.mutex) ); + mem3.aPool[i].u.list.next = *pRoot; + mem3.aPool[i].u.list.prev = 0; + if( *pRoot ){ + mem3.aPool[*pRoot].u.list.prev = i; + } + *pRoot = i; +} + +/* +** Link the chunk at index i into either the appropriate +** small chunk list, or into the large chunk hash table. +*/ +static void memsys3Link(u32 i){ + u32 size, hash; + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( i>=1 ); + assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 ); + size = mem3.aPool[i-1].u.hdr.size4x/4; + assert( size==mem3.aPool[i+size-1].u.hdr.prevSize ); + assert( size>=2 ); + if( size <= MX_SMALL ){ + memsys3LinkIntoList(i, &mem3.aiSmall[size-2]); + }else{ + hash = size % N_HASH; + memsys3LinkIntoList(i, &mem3.aiHash[hash]); + } +} + +/* +** If the STATIC_MEM mutex is not already held, obtain it now. The mutex +** will already be held (obtained by code in malloc.c) if +** sqlite3GlobalConfig.bMemStat is true. +*/ +static void memsys3Enter(void){ + if( sqlite3GlobalConfig.bMemstat==0 && mem3.mutex==0 ){ + mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM); + } + sqlite3_mutex_enter(mem3.mutex); +} +static void memsys3Leave(void){ + sqlite3_mutex_leave(mem3.mutex); +} + +/* +** Called when we are unable to satisfy an allocation of nBytes. +*/ +static void memsys3OutOfMemory(int nByte){ + if( !mem3.alarmBusy ){ + mem3.alarmBusy = 1; + assert( sqlite3_mutex_held(mem3.mutex) ); + sqlite3_mutex_leave(mem3.mutex); + sqlite3_release_memory(nByte); + sqlite3_mutex_enter(mem3.mutex); + mem3.alarmBusy = 0; + } +} + + +/* +** Chunk i is a free chunk that has been unlinked. Adjust its +** size parameters for check-out and return a pointer to the +** user portion of the chunk. +*/ +static void *memsys3Checkout(u32 i, u32 nBlock){ + u32 x; + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( i>=1 ); + assert( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ); + assert( mem3.aPool[i+nBlock-1].u.hdr.prevSize==nBlock ); + x = mem3.aPool[i-1].u.hdr.size4x; + mem3.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2); + mem3.aPool[i+nBlock-1].u.hdr.prevSize = nBlock; + mem3.aPool[i+nBlock-1].u.hdr.size4x |= 2; + return &mem3.aPool[i]; +} + +/* +** Carve a piece off of the end of the mem3.iMaster free chunk. +** Return a pointer to the new allocation. Or, if the master chunk +** is not large enough, return 0. +*/ +static void *memsys3FromMaster(u32 nBlock){ + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( mem3.szMaster>=nBlock ); + if( nBlock>=mem3.szMaster-1 ){ + /* Use the entire master */ + void *p = memsys3Checkout(mem3.iMaster, mem3.szMaster); + mem3.iMaster = 0; + mem3.szMaster = 0; + mem3.mnMaster = 0; + return p; + }else{ + /* Split the master block. Return the tail. */ + u32 newi, x; + newi = mem3.iMaster + mem3.szMaster - nBlock; + assert( newi > mem3.iMaster+1 ); + mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = nBlock; + mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x |= 2; + mem3.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1; + mem3.szMaster -= nBlock; + mem3.aPool[newi-1].u.hdr.prevSize = mem3.szMaster; + x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2; + mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x; + if( mem3.szMaster < mem3.mnMaster ){ + mem3.mnMaster = mem3.szMaster; + } + return (void*)&mem3.aPool[newi]; + } +} + +/* +** *pRoot is the head of a list of free chunks of the same size +** or same size hash. In other words, *pRoot is an entry in either +** mem3.aiSmall[] or mem3.aiHash[]. +** +** This routine examines all entries on the given list and tries +** to coalesce each entries with adjacent free chunks. +** +** If it sees a chunk that is larger than mem3.iMaster, it replaces +** the current mem3.iMaster with the new larger chunk. In order for +** this mem3.iMaster replacement to work, the master chunk must be +** linked into the hash tables. That is not the normal state of +** affairs, of course. The calling routine must link the master +** chunk before invoking this routine, then must unlink the (possibly +** changed) master chunk once this routine has finished. +*/ +static void memsys3Merge(u32 *pRoot){ + u32 iNext, prev, size, i, x; + + assert( sqlite3_mutex_held(mem3.mutex) ); + for(i=*pRoot; i>0; i=iNext){ + iNext = mem3.aPool[i].u.list.next; + size = mem3.aPool[i-1].u.hdr.size4x; + assert( (size&1)==0 ); + if( (size&2)==0 ){ + memsys3UnlinkFromList(i, pRoot); + assert( i > mem3.aPool[i-1].u.hdr.prevSize ); + prev = i - mem3.aPool[i-1].u.hdr.prevSize; + if( prev==iNext ){ + iNext = mem3.aPool[prev].u.list.next; + } + memsys3Unlink(prev); + size = i + size/4 - prev; + x = mem3.aPool[prev-1].u.hdr.size4x & 2; + mem3.aPool[prev-1].u.hdr.size4x = size*4 | x; + mem3.aPool[prev+size-1].u.hdr.prevSize = size; + memsys3Link(prev); + i = prev; + }else{ + size /= 4; + } + if( size>mem3.szMaster ){ + mem3.iMaster = i; + mem3.szMaster = size; + } + } +} + +/* +** Return a block of memory of at least nBytes in size. +** Return NULL if unable. +** +** This function assumes that the necessary mutexes, if any, are +** already held by the caller. Hence "Unsafe". +*/ +static void *memsys3MallocUnsafe(int nByte){ + u32 i; + u32 nBlock; + u32 toFree; + + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( sizeof(Mem3Block)==8 ); + if( nByte<=12 ){ + nBlock = 2; + }else{ + nBlock = (nByte + 11)/8; + } + assert( nBlock>=2 ); + + /* STEP 1: + ** Look for an entry of the correct size in either the small + ** chunk table or in the large chunk hash table. This is + ** successful most of the time (about 9 times out of 10). + */ + if( nBlock <= MX_SMALL ){ + i = mem3.aiSmall[nBlock-2]; + if( i>0 ){ + memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]); + return memsys3Checkout(i, nBlock); + } + }else{ + int hash = nBlock % N_HASH; + for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){ + if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){ + memsys3UnlinkFromList(i, &mem3.aiHash[hash]); + return memsys3Checkout(i, nBlock); + } + } + } + + /* STEP 2: + ** Try to satisfy the allocation by carving a piece off of the end + ** of the master chunk. This step usually works if step 1 fails. + */ + if( mem3.szMaster>=nBlock ){ + return memsys3FromMaster(nBlock); + } + + + /* STEP 3: + ** Loop through the entire memory pool. Coalesce adjacent free + ** chunks. Recompute the master chunk as the largest free chunk. + ** Then try again to satisfy the allocation by carving a piece off + ** of the end of the master chunk. This step happens very + ** rarely (we hope!) + */ + for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){ + memsys3OutOfMemory(toFree); + if( mem3.iMaster ){ + memsys3Link(mem3.iMaster); + mem3.iMaster = 0; + mem3.szMaster = 0; + } + for(i=0; i=nBlock ){ + return memsys3FromMaster(nBlock); + } + } + } + + /* If none of the above worked, then we fail. */ + return 0; +} + +/* +** Free an outstanding memory allocation. +** +** This function assumes that the necessary mutexes, if any, are +** already held by the caller. Hence "Unsafe". +*/ +static void memsys3FreeUnsafe(void *pOld){ + Mem3Block *p = (Mem3Block*)pOld; + int i; + u32 size, x; + assert( sqlite3_mutex_held(mem3.mutex) ); + assert( p>mem3.aPool && p<&mem3.aPool[mem3.nPool] ); + i = p - mem3.aPool; + assert( (mem3.aPool[i-1].u.hdr.size4x&1)==1 ); + size = mem3.aPool[i-1].u.hdr.size4x/4; + assert( i+size<=mem3.nPool+1 ); + mem3.aPool[i-1].u.hdr.size4x &= ~1; + mem3.aPool[i+size-1].u.hdr.prevSize = size; + mem3.aPool[i+size-1].u.hdr.size4x &= ~2; + memsys3Link(i); + + /* Try to expand the master using the newly freed chunk */ + if( mem3.iMaster ){ + while( (mem3.aPool[mem3.iMaster-1].u.hdr.size4x&2)==0 ){ + size = mem3.aPool[mem3.iMaster-1].u.hdr.prevSize; + mem3.iMaster -= size; + mem3.szMaster += size; + memsys3Unlink(mem3.iMaster); + x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2; + mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x; + mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster; + } + x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2; + while( (mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x&1)==0 ){ + memsys3Unlink(mem3.iMaster+mem3.szMaster); + mem3.szMaster += mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x/4; + mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x; + mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster; + } + } +} + +/* +** Return the size of an outstanding allocation, in bytes. The +** size returned omits the 8-byte header overhead. This only +** works for chunks that are currently checked out. +*/ +static int memsys3Size(void *p){ + Mem3Block *pBlock; + if( p==0 ) return 0; + pBlock = (Mem3Block*)p; + assert( (pBlock[-1].u.hdr.size4x&1)!=0 ); + return (pBlock[-1].u.hdr.size4x&~3)*2 - 4; +} + +/* +** Round up a request size to the next valid allocation size. +*/ +static int memsys3Roundup(int n){ + if( n<=12 ){ + return 12; + }else{ + return ((n+11)&~7) - 4; + } +} + +/* +** Allocate nBytes of memory. +*/ +static void *memsys3Malloc(int nBytes){ + sqlite3_int64 *p; + assert( nBytes>0 ); /* malloc.c filters out 0 byte requests */ + memsys3Enter(); + p = memsys3MallocUnsafe(nBytes); + memsys3Leave(); + return (void*)p; +} + +/* +** Free memory. +*/ +static void memsys3Free(void *pPrior){ + assert( pPrior ); + memsys3Enter(); + memsys3FreeUnsafe(pPrior); + memsys3Leave(); +} + +/* +** Change the size of an existing memory allocation +*/ +static void *memsys3Realloc(void *pPrior, int nBytes){ + int nOld; + void *p; + if( pPrior==0 ){ + return sqlite3_malloc(nBytes); + } + if( nBytes<=0 ){ + sqlite3_free(pPrior); + return 0; + } + nOld = memsys3Size(pPrior); + if( nBytes<=nOld && nBytes>=nOld-128 ){ + return pPrior; + } + memsys3Enter(); + p = memsys3MallocUnsafe(nBytes); + if( p ){ + if( nOld>1)!=(size&1) ){ + fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]); + assert( 0 ); + break; + } + if( size&1 ){ + fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8); + }else{ + fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8, + i==mem3.iMaster ? " **master**" : ""); + } + } + for(i=0; i0; j=mem3.aPool[j].u.list.next){ + fprintf(out, " %p(%d)", &mem3.aPool[j], + (mem3.aPool[j-1].u.hdr.size4x/4)*8-8); + } + fprintf(out, "\n"); + } + for(i=0; i0; j=mem3.aPool[j].u.list.next){ + fprintf(out, " %p(%d)", &mem3.aPool[j], + (mem3.aPool[j-1].u.hdr.size4x/4)*8-8); + } + fprintf(out, "\n"); + } + fprintf(out, "master=%d\n", mem3.iMaster); + fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szMaster*8); + fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnMaster*8); + sqlite3_mutex_leave(mem3.mutex); + if( out==stdout ){ + fflush(stdout); + }else{ + fclose(out); + } +#else + UNUSED_PARAMETER(zFilename); +#endif +} + +/* +** This routine is the only routine in this file with external +** linkage. +** +** Populate the low-level memory allocation function pointers in +** sqlite3GlobalConfig.m with pointers to the routines in this file. The +** arguments specify the block of memory to manage. +** +** This routine is only called by sqlite3_config(), and therefore +** is not required to be threadsafe (it is not). +*/ +const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){ + static const sqlite3_mem_methods mempoolMethods = { + memsys3Malloc, + memsys3Free, + memsys3Realloc, + memsys3Size, + memsys3Roundup, + memsys3Init, + memsys3Shutdown, + 0 + }; + return &mempoolMethods; +} + +#endif /* SQLITE_ENABLE_MEMSYS3 */ -- cgit v1.2.3