X-Git-Url: https://pd.if.org/git/?p=nbds;a=blobdiff_plain;f=struct%2Fht.c;h=704443550f686776b5d98ff887163b7e8659c607;hp=8d5e1600e3ad6d5441bcec4baf4c52fa6fff6b33;hb=af2000653f50ce43e94bfd260ce47e4b53ab2222;hpb=4a7804bd08c790fc3c4233312e4b485c3302fe02 diff --git a/struct/ht.c b/struct/ht.c index 8d5e160..7044435 100644 --- a/struct/ht.c +++ b/struct/ht.c @@ -16,7 +16,6 @@ #include "ht.h" #include "murmur.h" #include "mem.h" -#include "rcu.h" #define COPIED_VALUE (-1) #define TOMBSTONE STRIP_TAG(COPIED_VALUE) @@ -26,9 +25,11 @@ #define MIN_SCALE (__builtin_ctz(ENTRIES_PER_BUCKET) + 2) // min 4 buckets #define MAX_BUCKETS_TO_PROBE 250 +#define GET_PTR(x) ((string_t *)((x) & MASK(48))) // low-order 48 bits is a pointer to a string_t + typedef struct ht_entry { - int64_t key; - int64_t value; + uint64_t key; + uint64_t value; } entry_t; typedef struct string { @@ -49,7 +50,7 @@ typedef struct hash_table_i { } hash_table_i_t; static int hti_copy_entry - (hash_table_i_t *old_hti, volatile entry_t *e, uint32_t e_key_hash, hash_table_i_t *new_hti); + (hash_table_i_t *ht1, volatile entry_t *e, uint32_t e_key_hash, hash_table_i_t *ht2); // Choose the next bucket to probe using the high-order bits of . static inline int get_next_ndx(int old_ndx, uint32_t key_hash, int ht_scale) { @@ -66,7 +67,7 @@ static inline int get_next_ndx(int old_ndx, uint32_t key_hash, int ht_scale) { static inline int ht_key_equals (uint64_t a, uint32_t b_hash, const char *b_value, uint32_t b_len) { if ((b_hash >> 16) != (a >> 48)) // high-order 16 bits are from the hash value return FALSE; - const string_t *a_key = (string_t *)(a & MASK(48)); // low-order 48 bits is a pointer + const string_t *a_key = GET_PTR(a); assert(a_key); return a_key->len == b_len && memcmp(a_key->val, b_value, b_len) == 0; } @@ -80,34 +81,31 @@ static inline int ht_key_equals (uint64_t a, uint32_t b_hash, const char *b_valu // Record if the entry being returned is empty. Otherwise the caller will have to waste time with // ht_key_equals() to confirm that it did not lose a race to fill an empty entry. static volatile entry_t *hti_lookup (hash_table_i_t *hti, uint32_t key_hash, const char *key_val, uint32_t key_len, int *is_empty) { - TRACE("h0", "hti_lookup(key \"%s\" in hti %p)", key_val, hti); + TRACE("h0", "hti_lookup(key %p in hti %p)", key_val, hti); *is_empty = 0; // Probe one cache line at a time int ndx = key_hash & MASK(hti->scale); // the first entry to search - int i; - for (i = 0; i < hti->max_probe; ++i) { + for (int i = 0; i < hti->max_probe; ++i) { // The start of the bucket is the first entry in the cache line. volatile entry_t *bucket = hti->table + (ndx & ~(ENTRIES_PER_BUCKET-1)); // Start searching at the indexed entry. Then loop around to the begining of the cache line. - int j; - for (j = 0; j < ENTRIES_PER_BUCKET; ++j) { + for (int j = 0; j < ENTRIES_PER_BUCKET; ++j) { volatile entry_t *e = bucket + ((ndx + j) & (ENTRIES_PER_BUCKET-1)); uint64_t e_key = e->key; if (e_key == DOES_NOT_EXIST) { - TRACE("h0", "hti_lookup: empty entry %p found on probe %d", e, i*ENTRIES_PER_BUCKET+j+1); - // we tag the pointer so the caller can avoid an expensive ht_key_equals() - *is_empty = 1; + TRACE("h0", "hti_lookup: empty entry %p found", e, 0); + *is_empty = 1; // indicate an empty so the caller avoids an expensive ht_key_equals return e; } if (ht_key_equals(e_key, key_hash, key_val, key_len)) { - TRACE("h0", "hti_lookup: entry %p found on probe %d", e, i*ENTRIES_PER_BUCKET+j+1); - TRACE("h0", "hti_lookup: with key \"%s\" value %p", - ((string_t *)(e_key & MASK(48)))->val, e->value); + TRACE("h0", "hti_lookup: entry %p found value %p", e, e->value); + TRACE("h0", "hti_lookup: entry key %p len %llu", GET_PTR(e_key)->val, + GET_PTR(e_key)->len); return e; } } @@ -153,9 +151,7 @@ static hash_table_i_t *hti_alloc (hash_table_t *parent, int scale) { // // Initiates a copy by creating a larger hash_table_i_t and installing it in next>. static void hti_start_copy (hash_table_i_t *hti) { - TRACE("h0", "hti_start_copy(hti %p hti->next %p)", hti, hti->next); - if (hti->next) - return; // another thread beat us to it + TRACE("h0", "hti_start_copy(hti %p scale %llu)", hti, hti->scale); // heuristics to determine the size of the new table uint64_t count = ht_count(hti->ht); @@ -164,7 +160,8 @@ static void hti_start_copy (hash_table_i_t *hti) { new_scale += (count > (1 << (new_scale - 2))); // double size again if more than 1/2 full // Allocate the new table and attempt to install it. - hash_table_i_t *next = hti_alloc(hti->ht, hti->scale + 1); + hash_table_i_t *next = hti_alloc(hti->ht, new_scale); + TRACE("h0", "hti_start_copy: new hti %p scale %llu", next->scale, next->scale); hash_table_i_t *old_next = SYNC_CAS(&hti->next, NULL, next); if (old_next != NULL) { TRACE("h0", "hti_start_copy: lost race to install new hti; found %p", old_next, 0); @@ -175,31 +172,32 @@ static void hti_start_copy (hash_table_i_t *hti) { TRACE("h0", "hti_start_copy: new hti is %p", next, 0); } -// Copy the key and value stored in (which must be an entry in ) to . +// Copy the key and value stored in (which must be an entry in ) to . // -// Return 1 unless is already copied (then return 0), so the caller can account for the total +// Return 1 unless is already copied (then return 0), so the caller can account for the total // number of entries left to copy. -static int hti_copy_entry (hash_table_i_t *old_hti, volatile entry_t *old_e, uint32_t key_hash, - hash_table_i_t *new_hti) { - TRACE("h0", "hti_copy_entry(copy entry from %p to %p)", old_hti, new_hti); - assert(old_hti); - assert(old_hti->next); - assert(new_hti); - assert(old_e >= old_hti->table && old_e < old_hti->table + (1 << old_hti->scale)); - - int64_t old_e_value = old_e->value; - TRACE("h0", "hti_copy_entry: entry %p current value %p", old_e, old_e_value); - if (EXPECT_FALSE(old_e_value == COPIED_VALUE)) +static int hti_copy_entry (hash_table_i_t *ht1, volatile entry_t *ht1_e, uint32_t key_hash, + hash_table_i_t *ht2) { + TRACE("h0", "hti_copy_entry(copy entry from %p to %p)", ht1, ht2); + assert(ht1); + assert(ht1->next); + assert(ht2); + assert(ht1_e >= ht1->table && ht1_e < ht1->table + (1 << ht1->scale)); + assert(key_hash == 0 || (key_hash >> 16) == (ht1_e->key >> 48)); + + uint64_t ht1_e_value = ht1_e->value; + TRACE("h0", "hti_copy_entry: entry %p current value %p", ht1_e, ht1_e_value); + if (EXPECT_FALSE(ht1_e_value == COPIED_VALUE)) return FALSE; // already copied // Kill empty entries. - if (EXPECT_FALSE(old_e_value == DOES_NOT_EXIST)) { - old_e_value = SYNC_CAS(&old_e->value, DOES_NOT_EXIST, COPIED_VALUE); - if (old_e_value == DOES_NOT_EXIST) { + if (EXPECT_FALSE(ht1_e_value == DOES_NOT_EXIST)) { + uint64_t ht1_e_value = SYNC_CAS(&ht1_e->value, DOES_NOT_EXIST, COPIED_VALUE); + if (ht1_e_value == DOES_NOT_EXIST) { TRACE("h0", "hti_copy_entry: old entry killed", 0, 0); return TRUE; } - if (old_e_value == COPIED_VALUE) { + if (ht1_e_value == COPIED_VALUE) { TRACE("h0", "hti_copy_entry: lost race to kill empty entry in old hti", 0, 0); return FALSE; // another thread beat us to it } @@ -208,72 +206,74 @@ static int hti_copy_entry (hash_table_i_t *old_hti, volatile entry_t *old_e, uin } // Tag the value in the old entry to indicate a copy is in progress. - old_e_value = SYNC_FETCH_AND_OR(&old_e->value, TAG_VALUE(0)); - TRACE("h0", "hti_copy_entry: tagged the value %p in old entry %p", old_e_value, old_e); - if (old_e_value == COPIED_VALUE) + ht1_e_value = SYNC_FETCH_AND_OR(&ht1_e->value, TAG_VALUE(0)); + TRACE("h0", "hti_copy_entry: tagged the value %p in old entry %p", ht1_e_value, ht1_e); + if (ht1_e_value == COPIED_VALUE) return FALSE; // was already copied by another thread. // Deleted entries don't need to be installed into to the new table, but their keys do need to // be freed. assert(COPIED_VALUE == TAG_VALUE(TOMBSTONE)); - if (old_e_value == TOMBSTONE) { - nbd_free((string_t *)(old_e->key & MASK(48))); + if (ht1_e_value == TOMBSTONE) { + nbd_defer_free(GET_PTR(ht1_e->key)); return TRUE; } - old_e_value = STRIP_TAG(old_e_value); // Install the key in the new table. - uint64_t old_e_key = old_e->key; - string_t *key = (string_t *)(old_e_key & MASK(48)); - TRACE("h0", "hti_copy_entry: key %p is %s", old_e_key, key->val); + uint64_t key = ht1_e->key; + string_t *key_string = GET_PTR(key); + uint64_t value = STRIP_TAG(ht1_e_value); + TRACE("h0", "hti_copy_entry: key %p value %p", key, value); // We use 0 to indicate that isn't initiallized. Occasionally the will // really be 0 and we will waste time recomputing it. That is rare enough that it is OK. if (key_hash == 0) { - key_hash = murmur32(key->val, key->len); + key_hash = murmur32(key_string->val, key_string->len); } int is_empty; - volatile entry_t *new_e = hti_lookup(new_hti, key_hash, key->val, key->len, &is_empty); + volatile entry_t *ht2_e = hti_lookup(ht2, key_hash, key_string->val, key_string->len, &is_empty); // it is possible that there is not any room in the new table either - if (EXPECT_FALSE(new_e == NULL)) { - hti_start_copy(new_hti); // initiate nested copy, if not already started - return hti_copy_entry(old_hti, old_e, key_hash, new_hti->next); // recursive tail-call + if (EXPECT_FALSE(ht2_e == NULL)) { + if (ht2->next == NULL) { + hti_start_copy(ht2); // initiate nested copy, if not already started + } + return hti_copy_entry(ht1, ht1_e, key_hash, ht2->next); // recursive tail-call } // a tagged entry returned from hti_lookup() means it is either empty or has a new key if (is_empty) { - uint64_t new_e_key = SYNC_CAS(&new_e->key, DOES_NOT_EXIST, old_e_key); - if (new_e_key != DOES_NOT_EXIST) { + uint64_t old_ht2_e_key = SYNC_CAS(&ht2_e->key, DOES_NOT_EXIST, key); + if (old_ht2_e_key != DOES_NOT_EXIST) { TRACE("h0", "hti_copy_entry: lost race to CAS key %p into new entry; found %p", - old_e_key, new_e_key); - return hti_copy_entry(old_hti, old_e, key_hash, new_hti); // recursive tail-call + key, old_ht2_e_key); + return hti_copy_entry(ht1, ht1_e, key_hash, ht2); // recursive tail-call } } - assert(ht_key_equals(new_e->key, key_hash, key->val, key->len)); - TRACE("h0", "hti_copy_entry: key %p installed in new old hti %p", key->val, new_hti); + assert(ht_key_equals(ht2_e->key, key_hash, key_string->val, key_string->len)); + TRACE("h0", "hti_copy_entry: key %p installed in new hti %p", key_string->val, ht2); // Copy the value to the entry in the new table. - uint64_t new_e_value = SYNC_CAS(&new_e->value, DOES_NOT_EXIST, old_e_value); + uint64_t old_ht2_e_value = SYNC_CAS(&ht2_e->value, DOES_NOT_EXIST, value); // If there is a nested copy in progress, we might have installed the key into a dead entry. - if (new_e_value == COPIED_VALUE) - return hti_copy_entry(old_hti, old_e, key_hash, new_hti->next); // recursive tail-call + if (old_ht2_e_value == COPIED_VALUE) + return hti_copy_entry(ht1, ht1_e, key_hash, ht2->next); // recursive tail-call // Mark the old entry as dead. - old_e->value = COPIED_VALUE; + ht1_e->value = COPIED_VALUE; // Update the count if we were the one that completed the copy. - if (new_e_value == DOES_NOT_EXIST) { - TRACE("h0", "hti_copy_entry: value %p installed in new hti %p", old_e_value, new_hti); - SYNC_ADD(&old_hti->count, -1); - SYNC_ADD(&new_hti->count, 1); + if (old_ht2_e_value == DOES_NOT_EXIST) { + TRACE("h0", "hti_copy_entry: value %p installed in new hti %p", value, ht2); + SYNC_ADD(&ht1->count, -1); + SYNC_ADD(&ht2->count, 1); return TRUE; } TRACE("h0", "hti_copy_entry: lost race to CAS value %p in new hti; found %p", - old_e_value, new_e_value); + value, old_ht2_e_value); return FALSE; // another thread completed the copy } @@ -291,10 +291,10 @@ static int hti_copy_entry (hash_table_i_t *old_hti, volatile entry_t *old_e, uin // real value matches (i.e. not a TOMBSTONE or DOES_NOT_EXIST) as long as is in the table. If // is HT_EXPECT_WHATEVER then skip the test entirely. // -static int64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, const char *key_val, - uint32_t key_len, int64_t expected, int64_t new) { - TRACE("h0", "hti_compare_and_set(hti %p key \"%s\")", hti, key_val); - TRACE("h0", "hti_compare_and_set(new value %p; caller expects value %p)", new, expected); +static uint64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, const char *key_val, + uint32_t key_len, uint64_t expected, uint64_t new) { + TRACE("h0", "hti_compare_and_set: hti %p key %p", hti, key_val); + TRACE("h0", "hti_compare_and_set: new value %p expected old value %p", new, expected); assert(hti); assert(new != DOES_NOT_EXIST && !IS_TAGGED(new)); assert(key_val); @@ -304,7 +304,9 @@ static int64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, cons // There is no room for , grow the table and try again. if (e == NULL) { - hti_start_copy(hti); + if (hti->next == NULL) { + hti_start_copy(hti); + } return COPIED_VALUE; } @@ -318,26 +320,27 @@ static int64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, cons if (new == TOMBSTONE) return DOES_NOT_EXIST; - // allocate . + // Allocate . string_t *key = nbd_malloc(sizeof(uint32_t) + key_len); key->len = key_len; memcpy(key->val, key_val, key_len); - // CAS into the table. - uint64_t e_key = SYNC_CAS(&e->key, DOES_NOT_EXIST, ((uint64_t)(key_hash >> 16) << 48) | (uint64_t)key); + // Combine pointer with bits from its hash, CAS it into the table. + uint64_t temp = ((uint64_t)(key_hash >> 16) << 48) | (uint64_t)key; + uint64_t e_key = SYNC_CAS(&e->key, DOES_NOT_EXIST, temp); // Retry if another thread stole the entry out from under us. if (e_key != DOES_NOT_EXIST) { - TRACE("h0", "hti_compare_and_set: key in entry %p is \"%s\"", e, e_key & MASK(48)); - TRACE("h0", "hti_compare_and_set: lost race to install key \"%s\" in %p", key->val, e); + TRACE("h0", "hti_compare_and_set: lost race to install key %p in entry %p", key, e); + TRACE("h0", "hti_compare_and_set: found %p instead of NULL", GET_PTR(e_key), 0); nbd_free(key); return hti_compare_and_set(hti, key_hash, key_val, key_len, expected, new); // tail-call } - TRACE("h0", "hti_compare_and_set: installed key \"%s\" in entry %p", key_val, e); + TRACE("h0", "hti_compare_and_set: installed key %p in entry %p", key, e); } // If the entry is in the middle of a copy, the copy must be completed first. - int64_t e_value = e->value; + uint64_t e_value = e->value; TRACE("h0", "hti_compare_and_set: value in entry %p is %p", e, e_value); if (EXPECT_FALSE(IS_TAGGED(e_value))) { int did_copy = hti_copy_entry(hti, e, key_hash, ((volatile hash_table_i_t *)hti)->next); @@ -351,8 +354,8 @@ static int64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, cons int old_existed = (e_value != TOMBSTONE && e_value != DOES_NOT_EXIST); if (EXPECT_FALSE(expected != HT_EXPECT_WHATEVER && expected != e_value)) { if (EXPECT_FALSE(expected != (old_existed ? HT_EXPECT_EXISTS : HT_EXPECT_NOT_EXISTS))) { - TRACE("h0", "hti_compare_and_set: value expected by caller for key \"%s\" not found; " - "found value %p", key_val, e_value); + TRACE("h0", "hti_compare_and_set: value %p expected by caller not found; found value %p", + expected, e_value); return e_value; } } @@ -377,7 +380,7 @@ static int64_t hti_compare_and_set (hash_table_i_t *hti, uint32_t key_hash, cons } // -static int64_t hti_get (hash_table_i_t *hti, uint32_t key_hash, const char *key_val, uint32_t key_len) { +static uint64_t hti_get (hash_table_i_t *hti, uint32_t key_hash, const char *key_val, uint32_t key_len) { assert(key_val); int is_empty; @@ -396,7 +399,7 @@ static int64_t hti_get (hash_table_i_t *hti, uint32_t key_hash, const char *key_ return DOES_NOT_EXIST; // If the entry is being copied, finish the copy and retry on the next table. - int64_t e_value = e->value; + uint64_t e_value = e->value; if (EXPECT_FALSE(IS_TAGGED(e_value))) { if (EXPECT_FALSE(e_value != COPIED_VALUE)) { int did_copy = hti_copy_entry(hti, e, key_hash, ((volatile hash_table_i_t *)hti)->next); @@ -411,14 +414,16 @@ static int64_t hti_get (hash_table_i_t *hti, uint32_t key_hash, const char *key_ } // -int64_t ht_get (hash_table_t *ht, const char *key_val, uint32_t key_len) { +uint64_t ht_get (hash_table_t *ht, const char *key_val, uint32_t key_len) { return hti_get(*ht, murmur32(key_val, key_len), key_val, key_len); } // -int64_t ht_compare_and_set (hash_table_t *ht, const char *key_val, uint32_t key_len, - int64_t expected_val, int64_t new_val) { +uint64_t ht_compare_and_set (hash_table_t *ht, const char *key_val, uint32_t key_len, + uint64_t expected_val, uint64_t new_val) { + TRACE("h0", "ht_compare_and_set: key %p len %u", key_val, key_len); + TRACE("h0", "ht_compare_and_set: expected val %p new val %p", expected_val, new_val); assert(key_val); assert(!IS_TAGGED(new_val) && new_val != DOES_NOT_EXIST); @@ -426,38 +431,51 @@ int64_t ht_compare_and_set (hash_table_t *ht, const char *key_val, uint32_t key_ // Help with an ongoing copy. if (EXPECT_FALSE(hti->next != NULL)) { - - // Reserve some entries for this thread to copy. There is a race condition here because the - // fetch and add isn't atomic, but that is ok. + volatile entry_t *e; + uint64_t limit; + int num_copied = 0; int x = hti->scan; - hti->scan = x + ENTRIES_PER_COPY_CHUNK; - // scan> might be larger than the size of the table, if some thread stalls while - // copying. In that case we just wrap around to the begining and make another pass through - // the table. - volatile entry_t *e = hti->table + (x & MASK(hti->scale)); + TRACE("h0", "ht_compare_and_set: help copy. scan is %llu, size is %llu", x, 1<scale); + // Panic if we've been around the array twice and still haven't finished the copy. + int panic = (x >= (1 << (hti->scale + 1))); + if (!panic) { + limit = ENTRIES_PER_COPY_CHUNK; + + // Reserve some entries for this thread to copy. There is a race condition here because the + // fetch and add isn't atomic, but that is ok. + hti->scan = x + ENTRIES_PER_COPY_CHUNK; + + // scan> might be larger than the size of the table, if some thread stalls while + // copying. In that case we just wrap around to the begining and make another pass through + // the table. + e = hti->table + (x & MASK(hti->scale)); + } else { + TRACE("h0", "ht_compare_and_set: help copy panic", 0, 0); + // scan the whole table + limit = (1 << hti->scale); + e = hti->table; + } // Copy the entries - int num_copied = 0, i; - for (i = 0; i < ENTRIES_PER_COPY_CHUNK; ++i) { + for (int i = 0; i < limit; ++i) { num_copied += hti_copy_entry(hti, e++, 0, hti->next); assert(e <= hti->table + (1 << hti->scale)); } if (num_copied != 0) { SYNC_ADD(&hti->num_entries_copied, num_copied); } - } - // Dispose of fully copied tables. - while (hti->num_entries_copied == (1 << hti->scale)) { - assert(hti->next); - if (SYNC_CAS(ht, hti, hti->next) == hti) { - nbd_defer_free(hti); + // Dispose of fully copied tables. + if (hti->num_entries_copied == (1 << hti->scale) || panic) { + assert(hti->next); + if (SYNC_CAS(ht, hti, hti->next) == hti) { + nbd_defer_free(hti); + } } - hti = *ht; } - int64_t old_val; + uint64_t old_val; uint32_t key_hash = murmur32(key_val, key_len); while ((old_val = hti_compare_and_set(hti, key_hash, key_val, key_len, expected_val, new_val)) == COPIED_VALUE) { @@ -470,9 +488,9 @@ int64_t ht_compare_and_set (hash_table_t *ht, const char *key_val, uint32_t key_ // Remove the value in associated with . Returns the value removed, or // DOES_NOT_EXIST if there was no value for that key. -int64_t ht_remove (hash_table_t *ht, const char *key_val, uint32_t key_len) { +uint64_t ht_remove (hash_table_t *ht, const char *key_val, uint32_t key_len) { hash_table_i_t *hti = *ht; - int64_t val; + uint64_t val; uint32_t key_hash = murmur32(key_val, key_len); do { val = hti_compare_and_set(hti, key_hash, key_val, key_len, HT_EXPECT_WHATEVER, TOMBSTONE); @@ -506,6 +524,12 @@ hash_table_t *ht_alloc (void) { void ht_free (hash_table_t *ht) { hash_table_i_t *hti = *ht; do { + for (uint32_t i = 0; i < (1 << hti->scale); ++i) { + assert(hti->table[i].value == COPIED_VALUE || !IS_TAGGED(hti->table[i].value)); + if (hti->table[i].key != DOES_NOT_EXIST) { + nbd_free(GET_PTR(hti->table[i].key)); + } + } hash_table_i_t *next = hti->next; nbd_free(hti); hti = next;