diff options
Diffstat (limited to 'libnetdata/string/string.c')
| -rw-r--r-- | libnetdata/string/string.c | 595 |
1 files changed, 595 insertions, 0 deletions
diff --git a/libnetdata/string/string.c b/libnetdata/string/string.c new file mode 100644 index 000000000..a3f74b4ef --- /dev/null +++ b/libnetdata/string/string.c @@ -0,0 +1,595 @@ +// SPDX-License-Identifier: GPL-3.0-or-later + +#include "../libnetdata.h" +#include <Judy.h> + +typedef int32_t REFCOUNT; + +// ---------------------------------------------------------------------------- +// STRING implementation - dedup all STRING + +struct netdata_string { + uint32_t length; // the string length including the terminating '\0' + + REFCOUNT refcount; // how many times this string is used + // We use a signed number to be able to detect duplicate frees of a string. + // If at any point this goes below zero, we have a duplicate free. + + const char str[]; // the string itself, is appended to this structure +}; + +static struct string_hashtable { + Pvoid_t JudyHSArray; // the Judy array - hashtable + netdata_rwlock_t rwlock; // the R/W lock to protect the Judy array + + long int entries; // the number of entries in the index + long int active_references; // the number of active references alive + long int memory; // the memory used, without the JudyHS index + + size_t inserts; // the number of successful inserts to the index + size_t deletes; // the number of successful deleted from the index + size_t searches; // the number of successful searches in the index + size_t duplications; // when a string is referenced + size_t releases; // when a string is unreferenced + +#ifdef NETDATA_INTERNAL_CHECKS + // internal statistics + size_t found_deleted_on_search; + size_t found_available_on_search; + size_t found_deleted_on_insert; + size_t found_available_on_insert; + size_t spins; +#endif + +} string_base = { + .JudyHSArray = NULL, + .rwlock = NETDATA_RWLOCK_INITIALIZER, +}; + +#ifdef NETDATA_INTERNAL_CHECKS +#define string_internal_stats_add(var, val) __atomic_add_fetch(&string_base.var, val, __ATOMIC_RELAXED) +#else +#define string_internal_stats_add(var, val) do {;} while(0) +#endif + +#define string_stats_atomic_increment(var) __atomic_add_fetch(&string_base.var, 1, __ATOMIC_RELAXED) +#define string_stats_atomic_decrement(var) __atomic_sub_fetch(&string_base.var, 1, __ATOMIC_RELAXED) + +void string_statistics(size_t *inserts, size_t *deletes, size_t *searches, size_t *entries, size_t *references, size_t *memory, size_t *duplications, size_t *releases) { + *inserts = string_base.inserts; + *deletes = string_base.deletes; + *searches = string_base.searches; + *entries = (size_t)string_base.entries; + *references = (size_t)string_base.active_references; + *memory = (size_t)string_base.memory; + *duplications = string_base.duplications; + *releases = string_base.releases; +} + +#define string_entry_acquire(se) __atomic_add_fetch(&((se)->refcount), 1, __ATOMIC_SEQ_CST); +#define string_entry_release(se) __atomic_sub_fetch(&((se)->refcount), 1, __ATOMIC_SEQ_CST); + +static inline bool string_entry_check_and_acquire(STRING *se) { + REFCOUNT expected, desired, count = 0; + do { + count++; + + expected = __atomic_load_n(&se->refcount, __ATOMIC_SEQ_CST); + + if(expected <= 0) { + // We cannot use this. + // The reference counter reached value zero, + // so another thread is deleting this. + string_internal_stats_add(spins, count - 1); + return false; + } + + desired = expected + 1; + } + while(!__atomic_compare_exchange_n(&se->refcount, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)); + + string_internal_stats_add(spins, count - 1); + + // statistics + // string_base.active_references is altered at the in string_strdupz() and string_freez() + string_stats_atomic_increment(duplications); + + return true; +} + +STRING *string_dup(STRING *string) { + if(unlikely(!string)) return NULL; + +#ifdef NETDATA_INTERNAL_CHECKS + if(unlikely(__atomic_load_n(&string->refcount, __ATOMIC_SEQ_CST) <= 0)) + fatal("STRING: tried to %s() a string that is freed (it has %d references).", __FUNCTION__, string->refcount); +#endif + + string_entry_acquire(string); + + // statistics + string_stats_atomic_increment(active_references); + string_stats_atomic_increment(duplications); + + return string; +} + +// Search the index and return an ACQUIRED string entry, or NULL +static inline STRING *string_index_search(const char *str, size_t length) { + STRING *string; + + // Find the string in the index + // With a read-lock so that multiple readers can use the index concurrently. + + netdata_rwlock_rdlock(&string_base.rwlock); + + Pvoid_t *Rc; + Rc = JudyHSGet(string_base.JudyHSArray, (void *)str, length); + if(likely(Rc)) { + // found in the hash table + string = *Rc; + + if(string_entry_check_and_acquire(string)) { + // we can use this entry + string_internal_stats_add(found_available_on_search, 1); + } + else { + // this entry is about to be deleted by another thread + // do not touch it, let it go... + string = NULL; + string_internal_stats_add(found_deleted_on_search, 1); + } + } + else { + // not found in the hash table + string = NULL; + } + + string_stats_atomic_increment(searches); + netdata_rwlock_unlock(&string_base.rwlock); + + return string; +} + +// Insert a string to the index and return an ACQUIRED string entry, +// or NULL if the call needs to be retried (a deleted entry with the same key is still in the index) +// The returned entry is ACQUIRED, and it can either be: +// 1. a new item inserted, or +// 2. an item found in the index that is not currently deleted +static inline STRING *string_index_insert(const char *str, size_t length) { + STRING *string; + + netdata_rwlock_wrlock(&string_base.rwlock); + + STRING **ptr; + { + JError_t J_Error; + Pvoid_t *Rc = JudyHSIns(&string_base.JudyHSArray, (void *)str, length, &J_Error); + if (unlikely(Rc == PJERR)) { + fatal( + "STRING: Cannot insert entry with name '%s' to JudyHS, JU_ERRNO_* == %u, ID == %d", + str, + JU_ERRNO(&J_Error), + JU_ERRID(&J_Error)); + } + ptr = (STRING **)Rc; + } + + if (likely(*ptr == 0)) { + // a new item added to the index + size_t mem_size = sizeof(STRING) + length; + string = mallocz(mem_size); + strcpy((char *)string->str, str); + string->length = length; + string->refcount = 1; + *ptr = string; + string_base.inserts++; + string_base.entries++; + string_base.memory += (long)mem_size; + } + else { + // the item is already in the index + string = *ptr; + + if(string_entry_check_and_acquire(string)) { + // we can use this entry + string_internal_stats_add(found_available_on_insert, 1); + } + else { + // this entry is about to be deleted by another thread + // do not touch it, let it go... + string = NULL; + string_internal_stats_add(found_deleted_on_insert, 1); + } + + string_stats_atomic_increment(searches); + } + + netdata_rwlock_unlock(&string_base.rwlock); + return string; +} + +// delete an entry from the index +static inline void string_index_delete(STRING *string) { + netdata_rwlock_wrlock(&string_base.rwlock); + +#ifdef NETDATA_INTERNAL_CHECKS + if(unlikely(__atomic_load_n(&string->refcount, __ATOMIC_SEQ_CST) != 0)) + fatal("STRING: tried to delete a string at %s() that is already freed (it has %d references).", __FUNCTION__, string->refcount); +#endif + + bool deleted = false; + + if (likely(string_base.JudyHSArray)) { + JError_t J_Error; + int ret = JudyHSDel(&string_base.JudyHSArray, (void *)string->str, string->length, &J_Error); + if (unlikely(ret == JERR)) { + error( + "STRING: Cannot delete entry with name '%s' from JudyHS, JU_ERRNO_* == %u, ID == %d", + string->str, + JU_ERRNO(&J_Error), + JU_ERRID(&J_Error)); + } else + deleted = true; + } + + if (unlikely(!deleted)) + error("STRING: tried to delete '%s' that is not in the index. Ignoring it.", string->str); + else { + size_t mem_size = sizeof(STRING) + string->length; + string_base.deletes++; + string_base.entries--; + string_base.memory -= (long)mem_size; + freez(string); + } + + netdata_rwlock_unlock(&string_base.rwlock); +} + +STRING *string_strdupz(const char *str) { + if(unlikely(!str || !*str)) return NULL; + + size_t length = strlen(str) + 1; + STRING *string = string_index_search(str, length); + + while(!string) { + // The search above did not find anything, + // We loop here, because during insert we may find an entry that is being deleted by another thread. + // So, we have to let it go and retry to insert it again. + + string = string_index_insert(str, length); + } + + // statistics + string_stats_atomic_increment(active_references); + + return string; +} + +void string_freez(STRING *string) { + if(unlikely(!string)) return; + + REFCOUNT refcount = string_entry_release(string); + +#ifdef NETDATA_INTERNAL_CHECKS + if(unlikely(refcount < 0)) + fatal("STRING: tried to %s() a string that is already freed (it has %d references).", __FUNCTION__, string->refcount); +#endif + + if(unlikely(refcount == 0)) + string_index_delete(string); + + // statistics + string_stats_atomic_decrement(active_references); + string_stats_atomic_increment(releases); +} + +size_t string_strlen(STRING *string) { + if(unlikely(!string)) return 0; + return string->length - 1; +} + +const char *string2str(STRING *string) { + if(unlikely(!string)) return ""; + return string->str; +} + +STRING *string_2way_merge(STRING *a, STRING *b) { + static STRING *X = NULL; + + if(unlikely(!X)) { + X = string_strdupz("[x]"); + } + + if(unlikely(a == b)) return string_dup(a); + if(unlikely(a == X)) return string_dup(a); + if(unlikely(b == X)) return string_dup(b); + if(unlikely(!a)) return string_dup(X); + if(unlikely(!b)) return string_dup(X); + + size_t alen = string_strlen(a); + size_t blen = string_strlen(b); + size_t length = alen + blen + string_strlen(X) + 1; + char buf1[length + 1], buf2[length + 1], *dst1; + const char *s1, *s2; + + s1 = string2str(a); + s2 = string2str(b); + dst1 = buf1; + for( ; *s1 && *s2 && *s1 == *s2 ;s1++, s2++) + *dst1++ = *s1; + + *dst1 = '\0'; + + if(*s1 != '\0' || *s2 != '\0') { + *dst1++ = '['; + *dst1++ = 'x'; + *dst1++ = ']'; + + s1 = &(string2str(a))[alen - 1]; + s2 = &(string2str(b))[blen - 1]; + char *dst2 = &buf2[length]; + *dst2 = '\0'; + for (; *s1 && *s2 && *s1 == *s2; s1--, s2--) + *(--dst2) = *s1; + + strcpy(dst1, dst2); + } + + return string_strdupz(buf1); +} + +// ---------------------------------------------------------------------------- +// STRING unit test + +struct thread_unittest { + int join; + int dups; +}; + +static void *string_thread(void *arg) { + struct thread_unittest *tu = arg; + + for(; 1 ;) { + if(__atomic_load_n(&tu->join, __ATOMIC_RELAXED)) + break; + + STRING *s = string_strdupz("string thread checking 1234567890"); + + for(int i = 0; i < tu->dups ; i++) + string_dup(s); + + for(int i = 0; i < tu->dups ; i++) + string_freez(s); + + string_freez(s); + } + + return arg; +} + +static char **string_unittest_generate_names(size_t entries) { + char **names = mallocz(sizeof(char *) * entries); + for(size_t i = 0; i < entries ;i++) { + char buf[25 + 1] = ""; + snprintfz(buf, 25, "name.%zu.0123456789.%zu \t !@#$%%^&*(),./[]{}\\|~`", i, entries / 2 + i); + names[i] = strdupz(buf); + } + return names; +} + +static void string_unittest_free_char_pp(char **pp, size_t entries) { + for(size_t i = 0; i < entries ;i++) + freez(pp[i]); + + freez(pp); +} + +int string_unittest(size_t entries) { + size_t errors = 0; + + fprintf(stderr, "Generating %zu names and values...\n", entries); + char **names = string_unittest_generate_names(entries); + + // check string + { + long int string_entries_starting = string_base.entries; + + fprintf(stderr, "\nChecking strings...\n"); + + STRING *s1 = string_strdupz("hello unittest"); + STRING *s2 = string_strdupz("hello unittest"); + if(s1 != s2) { + errors++; + fprintf(stderr, "ERROR: duplicating strings are not deduplicated\n"); + } + else + fprintf(stderr, "OK: duplicating string are deduplicated\n"); + + STRING *s3 = string_dup(s1); + if(s3 != s1) { + errors++; + fprintf(stderr, "ERROR: cloning strings are not deduplicated\n"); + } + else + fprintf(stderr, "OK: cloning string are deduplicated\n"); + + if(s1->refcount != 3) { + errors++; + fprintf(stderr, "ERROR: string refcount is not 3\n"); + } + else + fprintf(stderr, "OK: string refcount is 3\n"); + + STRING *s4 = string_strdupz("world unittest"); + if(s4 == s1) { + errors++; + fprintf(stderr, "ERROR: string is sharing pointers on different strings\n"); + } + else + fprintf(stderr, "OK: string is properly handling different strings\n"); + + usec_t start_ut, end_ut; + STRING **strings = mallocz(entries * sizeof(STRING *)); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + strings[i] = string_strdupz(names[i]); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Created %zu strings in %llu usecs\n", entries, end_ut - start_ut); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + strings[i] = string_dup(strings[i]); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Cloned %zu strings in %llu usecs\n", entries, end_ut - start_ut); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + strings[i] = string_strdupz(string2str(strings[i])); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Found %zu existing strings in %llu usecs\n", entries, end_ut - start_ut); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + string_freez(strings[i]); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Released %zu referenced strings in %llu usecs\n", entries, end_ut - start_ut); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + string_freez(strings[i]); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Released (again) %zu referenced strings in %llu usecs\n", entries, end_ut - start_ut); + + start_ut = now_realtime_usec(); + for(size_t i = 0; i < entries ;i++) { + string_freez(strings[i]); + } + end_ut = now_realtime_usec(); + fprintf(stderr, "Freed %zu strings in %llu usecs\n", entries, end_ut - start_ut); + + freez(strings); + + if(string_base.entries != string_entries_starting + 2) { + errors++; + fprintf(stderr, "ERROR: strings dictionary should have %ld items but it has %ld\n", string_entries_starting + 2, string_base.entries); + } + else + fprintf(stderr, "OK: strings dictionary has 2 items\n"); + } + + // check 2-way merge + { + struct testcase { + char *src1; char *src2; char *expected; + } tests[] = { + { "", "", ""}, + { "a", "", "[x]"}, + { "", "a", "[x]"}, + { "a", "a", "a"}, + { "abcd", "abcd", "abcd"}, + { "foo_cs", "bar_cs", "[x]_cs"}, + { "cp_UNIQUE_INFIX_cs", "cp_unique_infix_cs", "cp_[x]_cs"}, + { "cp_UNIQUE_INFIX_ci_unique_infix_cs", "cp_unique_infix_ci_UNIQUE_INFIX_cs", "cp_[x]_cs"}, + { "foo[1234]", "foo[4321]", "foo[[x]]"}, + { NULL, NULL, NULL }, + }; + + for (struct testcase *tc = &tests[0]; tc->expected != NULL; tc++) { + STRING *src1 = string_strdupz(tc->src1); + STRING *src2 = string_strdupz(tc->src2); + STRING *expected = string_strdupz(tc->expected); + + STRING *result = string_2way_merge(src1, src2); + if (string_cmp(result, expected) != 0) { + fprintf(stderr, "string_2way_merge(\"%s\", \"%s\") -> \"%s\" (expected=\"%s\")\n", + string2str(src1), + string2str(src2), + string2str(result), + string2str(expected)); + errors++; + } + + string_freez(src1); + string_freez(src2); + string_freez(expected); + string_freez(result); + } + } + + // threads testing of string + { + struct thread_unittest tu = { + .dups = 1, + .join = 0, + }; + +#ifdef NETDATA_INTERNAL_CHECKS + size_t ofound_deleted_on_search = string_base.found_deleted_on_search, + ofound_available_on_search = string_base.found_available_on_search, + ofound_deleted_on_insert = string_base.found_deleted_on_insert, + ofound_available_on_insert = string_base.found_available_on_insert, + ospins = string_base.spins; +#endif + + size_t oinserts, odeletes, osearches, oentries, oreferences, omemory, oduplications, oreleases; + string_statistics(&oinserts, &odeletes, &osearches, &oentries, &oreferences, &omemory, &oduplications, &oreleases); + + time_t seconds_to_run = 5; + int threads_to_create = 2; + fprintf( + stderr, + "Checking string concurrency with %d threads for %lld seconds...\n", + threads_to_create, + (long long)seconds_to_run); + // check string concurrency + netdata_thread_t threads[threads_to_create]; + tu.join = 0; + for (int i = 0; i < threads_to_create; i++) { + char buf[100 + 1]; + snprintf(buf, 100, "string%d", i); + netdata_thread_create( + &threads[i], buf, NETDATA_THREAD_OPTION_DONT_LOG | NETDATA_THREAD_OPTION_JOINABLE, string_thread, &tu); + } + sleep_usec(seconds_to_run * USEC_PER_SEC); + + __atomic_store_n(&tu.join, 1, __ATOMIC_RELAXED); + for (int i = 0; i < threads_to_create; i++) { + void *retval; + netdata_thread_join(threads[i], &retval); + } + + size_t inserts, deletes, searches, sentries, references, memory, duplications, releases; + string_statistics(&inserts, &deletes, &searches, &sentries, &references, &memory, &duplications, &releases); + + fprintf(stderr, "inserts %zu, deletes %zu, searches %zu, entries %zu, references %zu, memory %zu, duplications %zu, releases %zu\n", + inserts - oinserts, deletes - odeletes, searches - osearches, sentries - oentries, references - oreferences, memory - omemory, duplications - oduplications, releases - oreleases); + +#ifdef NETDATA_INTERNAL_CHECKS + size_t found_deleted_on_search = string_base.found_deleted_on_search, + found_available_on_search = string_base.found_available_on_search, + found_deleted_on_insert = string_base.found_deleted_on_insert, + found_available_on_insert = string_base.found_available_on_insert, + spins = string_base.spins; + + fprintf(stderr, "on insert: %zu ok + %zu deleted\non search: %zu ok + %zu deleted\nspins: %zu\n", + found_available_on_insert - ofound_available_on_insert, + found_deleted_on_insert - ofound_deleted_on_insert, + found_available_on_search - ofound_available_on_search, + found_deleted_on_search - ofound_deleted_on_search, + spins - ospins + ); +#endif + } + + string_unittest_free_char_pp(names, entries); + + fprintf(stderr, "\n%zu errors found\n", errors); + return errors ? 1 : 0; +} |