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mdbx: change branch-node size to ~1/2 of the page size.

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Change-Id: I0f455ec04170d792ecc933aa501b4ec1ca9b08c0
This commit is contained in:
Leonid Yuriev 2021-03-25 16:13:26 +03:00
parent 72f3a2fc3f
commit bfc9921305
1 changed files with 10 additions and 6 deletions
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16
src/core.c
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@ -354,10 +354,13 @@ node_largedata_pgno(const MDBX_node *const __restrict node) {
* BRANCH_NODE_MAX
* Branch-page must contain at least two nodes, within each a key and a child
* page number. But page can't be splitted if it contains less that 4 keys,
* i.e. a page should not overflow before adding the fourth key.
* Therefore, at least 3 branch-node should fit in the single branch-page:
* i.e. a page should not overflow before adding the fourth key. Therefore,
* at least 3 branch-node should fit in the single branch-page. Further, the
* first node of a branch-page doesn't contain a key, i.e. the first node
* is always require space just for itself. Thus:
* PAGEROOM = pagesize - page_hdr_len;
* BRANCH_NODE_MAX = even_floor(PAGEROOM / 3 - sizeof(indx_t));
* BRANCH_NODE_MAX = even_floor(
* (PAGEROOM - sizeof(indx_t) - NODESIZE) / (3 - 1) - sizeof(indx_t));
* KEYLEN_MAX = BRANCH_NODE_MAX - node_hdr_len;
*
* LEAF_NODE_MAX
@ -386,7 +389,8 @@ node_largedata_pgno(const MDBX_node *const __restrict node) {
#define PAGEROOM(pagesize) ((pagesize)-PAGEHDRSZ)
#define EVEN_FLOOR(n) ((n) & ~(size_t)1)
#define BRANCH_NODE_MAX(pagesize) \
(EVEN_FLOOR(PAGEROOM(pagesize) / 3) - sizeof(indx_t))
(EVEN_FLOOR((PAGEROOM(pagesize) - sizeof(indx_t) - NODESIZE) / (3 - 1) - \
sizeof(indx_t)))
#define LEAF_NODE_MAX(pagesize) \
(EVEN_FLOOR(PAGEROOM(pagesize) / 2) - sizeof(indx_t))
#define MAX_GC1OVPAGE(pagesize) (PAGEROOM(pagesize) / sizeof(pgno_t) - 1)
@ -10428,7 +10432,7 @@ static void __cold mdbx_setup_pagesize(MDBX_env *env, const size_t pagesize) {
STATIC_ASSERT(LEAF_NODE_MAX(MIN_PAGESIZE) > sizeof(MDBX_db) + NODESIZE + 42);
STATIC_ASSERT(LEAF_NODE_MAX(MAX_PAGESIZE) < UINT16_MAX);
STATIC_ASSERT(LEAF_NODE_MAX(MIN_PAGESIZE) > BRANCH_NODE_MAX(MIN_PAGESIZE));
STATIC_ASSERT(LEAF_NODE_MAX(MIN_PAGESIZE) >= BRANCH_NODE_MAX(MIN_PAGESIZE));
STATIC_ASSERT(BRANCH_NODE_MAX(MAX_PAGESIZE) > NODESIZE + 42);
STATIC_ASSERT(BRANCH_NODE_MAX(MAX_PAGESIZE) < UINT16_MAX);
const intptr_t branch_nodemax = BRANCH_NODE_MAX(pagesize);
@ -10437,7 +10441,7 @@ static void __cold mdbx_setup_pagesize(MDBX_env *env, const size_t pagesize) {
branch_nodemax > (intptr_t)(NODESIZE + 42) &&
branch_nodemax % 2 == 0 &&
leaf_nodemax > (intptr_t)(sizeof(MDBX_db) + NODESIZE + 42) &&
leaf_nodemax > branch_nodemax &&
leaf_nodemax >= branch_nodemax &&
leaf_nodemax < (int)UINT16_MAX && leaf_nodemax % 2 == 0);
env->me_leaf_nodemax = (unsigned)leaf_nodemax;
env->me_psize2log = (uint8_t)log2n(pagesize);