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-rw-r--r--erts/emulator/beam/erl_db_hash.c67
1 files changed, 41 insertions, 26 deletions
diff --git a/erts/emulator/beam/erl_db_hash.c b/erts/emulator/beam/erl_db_hash.c
index 82f03e458a..2d24f438ca 100644
--- a/erts/emulator/beam/erl_db_hash.c
+++ b/erts/emulator/beam/erl_db_hash.c
@@ -89,10 +89,20 @@
*/
#define CHAIN_LEN 6 /* Medium bucket chain len */
-/* Number of slots per segment */
-#define SEGSZ_EXP 8
-#define SEGSZ (1 << SEGSZ_EXP)
-#define SEGSZ_MASK (SEGSZ-1)
+/*
+** We want the first mandatory segment to be small (to reduce minimal footprint)
+** and larger extra segments (to reduce number of alloc/free calls).
+*/
+
+/* Number of slots in first segment */
+#define FIRST_SEGSZ_EXP 8
+#define FIRST_SEGSZ (1 << FIRST_SEGSZ_EXP)
+#define FIRST_SEGSZ_MASK (FIRST_SEGSZ - 1)
+
+/* Number of slots per extra segment */
+#define EXT_SEGSZ_EXP 11
+#define EXT_SEGSZ (1 << EXT_SEGSZ_EXP)
+#define EXT_SEGSZ_MASK (EXT_SEGSZ-1)
#define NSEG_1 (ErtsSizeofMember(DbTableHash,first_segtab) / sizeof(struct segment*))
#define NSEG_2 256 /* Size of second segment table */
@@ -115,7 +125,9 @@
#define NACTIVE(tb) ((int)erts_smp_atomic_read_nob(&(tb)->nactive))
#define NITEMS(tb) ((int)erts_smp_atomic_read_nob(&(tb)->common.nitems))
-#define BUCKET(tb, i) SEGTAB(tb)[(i) >> SEGSZ_EXP]->buckets[(i) & SEGSZ_MASK]
+#define SLOT_IX_TO_SEG_IX(i) (((i)+(EXT_SEGSZ-FIRST_SEGSZ)) >> EXT_SEGSZ_EXP)
+
+#define BUCKET(tb, i) SEGTAB(tb)[SLOT_IX_TO_SEG_IX(i)]->buckets[(i) & EXT_SEGSZ_MASK]
/*
* When deleting a table, the number of records to delete.
@@ -422,7 +434,7 @@ db_finalize_dbterm_hash(int cret, DbUpdateHandle* handle);
static ERTS_INLINE void try_shrink(DbTableHash* tb)
{
int nactive = NACTIVE(tb);
- if (nactive > SEGSZ && NITEMS(tb) < (nactive * CHAIN_LEN)
+ if (nactive > FIRST_SEGSZ && NITEMS(tb) < (nactive * CHAIN_LEN)
&& !IS_FIXED(tb)) {
shrink(tb, nactive);
}
@@ -621,17 +633,17 @@ int db_create_hash(Process *p, DbTable *tbl)
{
DbTableHash *tb = &tbl->hash;
- erts_smp_atomic_init_nob(&tb->szm, SEGSZ_MASK);
- erts_smp_atomic_init_nob(&tb->nactive, SEGSZ);
+ erts_smp_atomic_init_nob(&tb->szm, FIRST_SEGSZ_MASK);
+ erts_smp_atomic_init_nob(&tb->nactive, FIRST_SEGSZ);
erts_smp_atomic_init_nob(&tb->fixdel, (erts_aint_t)NULL);
erts_smp_atomic_init_nob(&tb->segtab, (erts_aint_t)NULL);
SET_SEGTAB(tb, tb->first_segtab);
tb->nsegs = NSEG_1;
- tb->nslots = SEGSZ;
+ tb->nslots = FIRST_SEGSZ;
tb->first_segtab[0] = (struct segment*) erts_db_alloc(ERTS_ALC_T_DB_SEG,
(DbTable *) tb,
- SIZEOF_SEGMENT(SEGSZ));
- sys_memset(tb->first_segtab[0], 0, SIZEOF_SEGMENT(SEGSZ));
+ SIZEOF_SEGMENT(FIRST_SEGSZ));
+ sys_memset(tb->first_segtab[0], 0, SIZEOF_SEGMENT(FIRST_SEGSZ));
#ifdef ERTS_SMP
erts_smp_atomic_init_nob(&tb->is_resizing, 0);
@@ -649,7 +661,7 @@ int db_create_hash(Process *p, DbTable *tbl)
erts_smp_rwmtx_init_opt_x(&tb->locks->lck_vec[i].lck, &rwmtx_opt,
"db_hash_slot", make_small(i));
}
- /* This important property is needed to guarantee that the buckets
+ /* This important property is needed to guarantee the two buckets
* involved in a grow/shrink operation it protected by the same lock:
*/
ASSERT(erts_smp_atomic_read_nob(&tb->nactive) % DB_HASH_LOCK_CNT == 0);
@@ -2213,12 +2225,12 @@ static int db_free_table_continue_hash(DbTable *tbl)
done /= 2;
while(tb->nslots != 0) {
- free_seg(tb, 1);
+ done += 1 + EXT_SEGSZ/64 + free_seg(tb, 1);
/*
* If we have done enough work, get out here.
*/
- if (++done >= (DELETE_RECORD_LIMIT / CHAIN_LEN / SEGSZ)) {
+ if (done >= DELETE_RECORD_LIMIT) {
return 0; /* Not done */
}
}
@@ -2406,9 +2418,10 @@ static struct ext_segtab* alloc_ext_segtab(DbTableHash* tb, unsigned seg_ix)
*/
static int alloc_seg(DbTableHash *tb)
{
- int seg_ix = tb->nslots >> SEGSZ_EXP;
+ int seg_ix = SLOT_IX_TO_SEG_IX(tb->nslots);
struct segment** segtab;
+ ASSERT(seg_ix > 0);
if (seg_ix == tb->nsegs) { /* New segtab needed */
struct ext_segtab* est = alloc_ext_segtab(tb, seg_ix);
SET_SEGTAB(tb, est->segtab);
@@ -2418,9 +2431,9 @@ static int alloc_seg(DbTableHash *tb)
segtab = SEGTAB(tb);
segtab[seg_ix] = (struct segment*) erts_db_alloc(ERTS_ALC_T_DB_SEG,
(DbTable *) tb,
- SIZEOF_SEGMENT(SEGSZ));
- sys_memset(segtab[seg_ix], 0, SIZEOF_SEGMENT(SEGSZ));
- tb->nslots += SEGSZ;
+ SIZEOF_SEGMENT(EXT_SEGSZ));
+ sys_memset(segtab[seg_ix], 0, SIZEOF_SEGMENT(EXT_SEGSZ));
+ tb->nslots += EXT_SEGSZ;
return 1;
}
@@ -2438,9 +2451,10 @@ static void dealloc_ext_segtab(void* lop_data)
*/
static int free_seg(DbTableHash *tb, int free_records)
{
- const int seg_ix = (tb->nslots >> SEGSZ_EXP) - 1;
+ const int seg_ix = SLOT_IX_TO_SEG_IX(tb->nslots) - 1;
struct segment** const segtab = SEGTAB(tb);
struct segment* const segp = segtab[seg_ix];
+ Uint seg_sz;
int nrecords = 0;
ASSERT(segp != NULL);
@@ -2448,8 +2462,8 @@ static int free_seg(DbTableHash *tb, int free_records)
if (free_records)
#endif
{
- int i;
- for (i=0; i<SEGSZ; ++i) {
+ int i = (seg_ix == 0) ? FIRST_SEGSZ : EXT_SEGSZ;
+ while (i--) {
HashDbTerm* p = segp->buckets[i];
while(p != 0) {
HashDbTerm* nxt = p->next;
@@ -2495,13 +2509,14 @@ static int free_seg(DbTableHash *tb, int free_records)
}
}
- erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable *)tb, segp, SIZEOF_SEGMENT(SEGSZ));
+ seg_sz = (seg_ix == 0) ? FIRST_SEGSZ : EXT_SEGSZ;
+ erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable *)tb, segp, SIZEOF_SEGMENT(seg_sz));
#ifdef DEBUG
if (seg_ix < tb->nsegs)
SEGTAB(tb)[seg_ix] = NULL;
#endif
- tb->nslots -= SEGSZ;
+ tb->nslots -= seg_sz;
ASSERT(tb->nslots >= 0);
return nrecords;
}
@@ -2589,7 +2604,7 @@ static void grow(DbTableHash* tb, int nactive)
/* Ensure that the slot nactive exists */
if (nactive == tb->nslots) {
/* Time to get a new segment */
- ASSERT((nactive & SEGSZ_MASK) == 0);
+ ASSERT(((nactive-FIRST_SEGSZ) & EXT_SEGSZ_MASK) == 0);
if (!alloc_seg(tb)) goto abort;
}
ASSERT(nactive < tb->nslots);
@@ -2668,7 +2683,7 @@ static void shrink(DbTableHash* tb, int nactive)
int dst_ix = src_ix & low_szm;
ASSERT(dst_ix < src_ix);
- ASSERT(nactive > SEGSZ);
+ ASSERT(nactive > FIRST_SEGSZ);
lck = WLOCK_HASH(tb, dst_ix);
/* Double check for racing table fixers */
if (!IS_FIXED(tb)) {
@@ -2697,7 +2712,7 @@ static void shrink(DbTableHash* tb, int nactive)
}
WUNLOCK_HASH(lck);
- if (tb->nslots - src_ix >= SEGSZ) {
+ if (tb->nslots - src_ix >= EXT_SEGSZ) {
free_seg(tb, 0);
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-18 08:43:49 +0000