From 00096d4cda052f369bc5b9f8a0939d9fa7873a9b Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Thu, 24 May 2018 18:36:13 +0200 Subject: erts: Simplify cpool_fetch and avoid faulty bumps of 'entrance_removed' stat. --- erts/emulator/beam/erl_alloc_util.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) (limited to 'erts') diff --git a/erts/emulator/beam/erl_alloc_util.c b/erts/emulator/beam/erl_alloc_util.c index 1c95385649..f0e764c9a7 100644 --- a/erts/emulator/beam/erl_alloc_util.c +++ b/erts/emulator/beam/erl_alloc_util.c @@ -3370,8 +3370,7 @@ cpool_delete(Allctr_t *allctr, Allctr_t *prev_allctr, Carrier_t *crr) static Carrier_t * cpool_fetch(Allctr_t *allctr, UWord size) { - enum { IGNORANT, HAS_SEEN_SENTINEL, THE_LAST_ONE } loop_state; - int i; + int i, seen_sentinel; Carrier_t *crr; Carrier_t *reinsert_crr = NULL; ErtsAlcCPoolData_t *cpdp; @@ -3485,43 +3484,34 @@ cpool_fetch(Allctr_t *allctr, UWord size) /* * We saw a pooled carried above, use it as entrance into the pool */ - cpdp = cpool_entrance; } else { /* - * No pooled carried seen above. Start search at cpool sentinel, + * No pooled carrier seen above. Start search at cpool sentinel, * but begin by passing one element before trying to fetch. * This in order to avoid contention with threads inserting elements. */ - cpool_entrance = sentinel; - cpdp = cpool_aint2cpd(cpool_read(&cpool_entrance->prev)); - if (cpdp == sentinel) + cpool_entrance = cpool_aint2cpd(cpool_read(&sentinel->prev)); + if (cpool_entrance == sentinel) goto check_dc_list; } - loop_state = IGNORANT; + cpdp = cpool_entrance; + seen_sentinel = 0; do { erts_aint_t exp; cpdp = cpool_aint2cpd(cpool_read(&cpdp->prev)); - if (cpdp == cpool_entrance) { - if (cpool_entrance == sentinel) { - cpdp = cpool_aint2cpd(cpool_read(&cpdp->prev)); - if (cpdp == sentinel) - break; - } - loop_state = THE_LAST_ONE; - } - else if (cpdp == sentinel) { - if (loop_state == HAS_SEEN_SENTINEL) { + if (cpdp == sentinel) { + if (seen_sentinel) { /* We been here before. cpool_entrance must have been removed */ INC_CC(allctr->cpool.stat.entrance_removed); break; } - cpdp = cpool_aint2cpd(cpool_read(&cpdp->prev)); - if (cpdp == sentinel) - break; - loop_state = HAS_SEEN_SENTINEL; + seen_sentinel = 1; + continue; } + ASSERT(cpdp != cpool_entrance || seen_sentinel); + crr = ErtsContainerStruct(cpdp, Carrier_t, cpool); exp = erts_atomic_read_rb(&crr->allctr); @@ -3554,7 +3544,7 @@ cpool_fetch(Allctr_t *allctr, UWord size) INC_CC(allctr->cpool.stat.fail_shared); return NULL; } - }while (loop_state != THE_LAST_ONE); + }while (cpdp != cpool_entrance); check_dc_list: /* Last; check our own pending dealloc carrier list... */ -- cgit v1.2.3