From 5de9bdbb42874a8b2706a80f4977c6009dfabbbf Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Sat, 31 Jul 2021 03:20:56 +0200 Subject: [PATCH 4/4] Generation: allocChunkLimit --- src/backend/utils/mmgr/generation.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/src/backend/utils/mmgr/generation.c b/src/backend/utils/mmgr/generation.c index 6c90416e27..2c98877953 100644 --- a/src/backend/utils/mmgr/generation.c +++ b/src/backend/utils/mmgr/generation.c @@ -46,6 +46,8 @@ #define Generation_BLOCKHDRSZ MAXALIGN(sizeof(GenerationBlock)) #define Generation_CHUNKHDRSZ sizeof(GenerationChunk) +#define Generation_CHUNK_FRACTION 8 + typedef struct GenerationBlock GenerationBlock; /* forward reference */ typedef struct GenerationChunk GenerationChunk; @@ -63,6 +65,7 @@ typedef struct GenerationContext Size initBlockSize; /* initial block size */ Size maxBlockSize; /* maximum block size */ Size nextBlockSize; /* next block size to allocate */ + Size allocChunkLimit; /* effective chunk size limit */ GenerationBlock *block; /* current (most recently allocated) block */ GenerationBlock *keeper; /* keeper block */ @@ -254,6 +257,17 @@ GenerationContextCreate(MemoryContext parent, set->initBlockSize = initBlockSize; set->maxBlockSize = maxBlockSize; set->nextBlockSize = initBlockSize; + + /* + * Compute the allocation chunk size limit for this context. + * + * Follows similar ideas as AllocSet, see aset.c for details ... + */ + set->allocChunkLimit = maxBlockSize; + while ((Size) (set->allocChunkLimit + Generation_CHUNKHDRSZ) > + (Size) ((Size) (maxBlockSize - Generation_BLOCKHDRSZ) / Generation_CHUNK_FRACTION)) + set->allocChunkLimit >>= 1; + set->block = NULL; set->keeper = NULL; dlist_init(&set->blocks); @@ -345,12 +359,9 @@ GenerationAlloc(MemoryContext context, Size size) GenerationBlock *block; GenerationChunk *chunk; Size chunk_size = MAXALIGN(size); - Size blockSize; - - blockSize = set->initBlockSize; /* is it an over-sized chunk? if yes, allocate special block */ - if (chunk_size > (blockSize / 8)) + if (chunk_size > set->allocChunkLimit) { Size blksize = chunk_size + Generation_BLOCKHDRSZ + Generation_CHUNKHDRSZ; @@ -427,6 +438,7 @@ GenerationAlloc(MemoryContext context, Size size) (block->endptr - block->freeptr) < Generation_CHUNKHDRSZ + chunk_size) { Size blksize; + Size required_size; /* * The first such block has size initBlockSize, and we double the @@ -437,6 +449,14 @@ GenerationAlloc(MemoryContext context, Size size) if (set->nextBlockSize > set->maxBlockSize) set->nextBlockSize = set->maxBlockSize; + /* + * If initBlockSize is less than ALLOC_CHUNK_LIMIT, we could need more + * space... but try to keep it a power of 2. + */ + required_size = chunk_size + Generation_BLOCKHDRSZ + Generation_CHUNKHDRSZ; + while (blksize < required_size) + blksize <<= 1; + block = (GenerationBlock *) malloc(blksize); if (block == NULL) -- 2.31.1