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chg: dev: Remove zero initialization of large buffers

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Profiles show that an high amount of CPU time spent in memset.
By removing zero initalization of certain large buffers we improve
performance in certain authoritative workloads.

Closes #5159

Merge branch '5159-do-not-zero-qp-search-buffers' into 'main'

See merge request isc-projects/bind9!10058
This commit is contained in:
Alessio Podda
2025-04-02 15:00:34 +00:00
parent 9d4bf476d8 4017a40b1d
commit b407f9caa8
3 changed files with 78 additions and 21 deletions
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29
lib/dns/qp.c
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@@ -1785,10 +1785,14 @@ dns_qpchain_init(dns_qpreadable_t qpr, dns_qpchain_t *chain) {
REQUIRE(QP_VALID(qp));
REQUIRE(chain != NULL);
*chain = (dns_qpchain_t){
.magic = QPCHAIN_MAGIC,
.qp = qp,
};
/*
* dns_qpchain_t contains a 2kb buffer, which is slow to
* zero-initialize. Therefore we avoid designated initializers, and
* initialize each field manually.
*/
chain->magic = QPCHAIN_MAGIC;
chain->qp = qp;
chain->len = 0;
}
unsigned int
@@ -1821,10 +1825,19 @@ dns_qpiter_init(dns_qpreadable_t qpr, dns_qpiter_t *qpi) {
dns_qpreader_t *qp = dns_qpreader(qpr);
REQUIRE(QP_VALID(qp));
REQUIRE(qpi != NULL);
*qpi = (dns_qpiter_t){
.qp = qp,
.magic = QPITER_MAGIC,
};
/*
* dns_qpiter_t contains a 4kb buffer, which is slow to zero-initialize.
* Therefore we avoid designated initializers, and initialize each
* field manually.
*/
qpi->qp = qp;
qpi->sp = 0;
qpi->magic = QPITER_MAGIC;
/*
* The top of the stack must be initialized.
*/
qpi->stack[qpi->sp] = NULL;
}
/*

31
lib/dns/qpcache.c
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@@ -1458,6 +1458,29 @@ find_coveringnsec(qpc_search_t *search, const dns_name_t *name,
(DNS_TRUST_PENDING((found)->trust) && \
(((options) & DNS_DBFIND_PENDINGOK) == 0)))
static void
qpc_search_init(qpc_search_t *search, qpcache_t *db, unsigned int options,
isc_stdtime_t now) {
/*
* qpc_search_t contains two structures with large buffers (dns_qpiter_t
* and dns_qpchain_t). Those two structures will be initialized later by
* dns_qp_lookup anyway.
* To avoid the overhead of zero initialization, we avoid designated
* initializers and initialize all "small" fields manually.
*/
search->qpdb = (qpcache_t *)db;
search->options = options;
/*
* qpch->in - Init by dns_qp_lookup
* qpiter - Init by dns_qp_lookup
*/
search->need_cleanup = false;
search->now = now ? now : isc_stdtime_now();
search->zonecut = NULL;
search->zonecut_header = NULL;
search->zonecut_sigheader = NULL;
}
static isc_result_t
qpcache_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
dns_rdatatype_t type, unsigned int options, isc_stdtime_t __now,
@@ -1479,11 +1502,9 @@ qpcache_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
dns_slabheader_t *foundsig = NULL, *nssig = NULL, *cnamesig = NULL;
dns_slabheader_t *nsecheader = NULL, *nsecsig = NULL;
dns_typepair_t sigtype, negtype;
qpc_search_t search = (qpc_search_t){
.qpdb = (qpcache_t *)db,
.options = options,
.now = __now ? __now : isc_stdtime_now(),
};
qpc_search_t search;
qpc_search_init(&search, (qpcache_t *)db, options, __now);
REQUIRE(VALID_QPDB((qpcache_t *)db));
REQUIRE(version == NULL);

39
lib/dns/qpzone.c
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@@ -3326,6 +3326,34 @@ qpzone_check_zonecut(qpznode_t *node, void *arg DNS__DB_FLARG) {
return result;
}
static void
qpz_search_init(qpz_search_t *search, qpzonedb_t *db, qpz_version_t *version,
unsigned int options) {
/*
* qpz_search_t contains two structures with large buffers (dns_qpiter_t
* and dns_qpchain_t). Those two structures will be initialized later by
* dns_qp_lookup anyway.
* To avoid the overhead of zero initialization, we avoid designated
* initializers and initialize all "small" fields manually.
*/
search->qpdb = db;
search->version = version;
search->qpr = (dns_qpread_t){};
search->serial = version->serial;
search->options = options;
/*
* qpch->in -- init in dns_qp_lookup
* qpiter -- init in dns_qp_lookup
*/
search->copy_name = false;
search->need_cleanup = false;
search->wild = false;
search->zonecut = NULL;
search->zonecut_header = NULL;
search->zonecut_sigheader = NULL;
dns_fixedname_init(&search->zonecut_name);
}
static isc_result_t
qpzone_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
dns_rdatatype_t type, unsigned int options,
@@ -3335,7 +3363,6 @@ qpzone_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
isc_result_t result;
qpzonedb_t *qpdb = (qpzonedb_t *)db;
qpznode_t *node = NULL;
qpz_search_t search;
bool cname_ok = true, close_version = false;
bool maybe_zonecut = false, at_zonecut = false;
bool wild = false, empty_node = false;
@@ -3361,13 +3388,9 @@ qpzone_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
close_version = true;
}
search = (qpz_search_t){
.qpdb = (qpzonedb_t *)db,
.version = (qpz_version_t *)version,
.serial = ((qpz_version_t *)version)->serial,
.options = options,
};
dns_fixedname_init(&search.zonecut_name);
qpz_search_t search;
qpz_search_init(&search, (qpzonedb_t *)db, (qpz_version_t *)version,
options);
if ((options & DNS_DBFIND_FORCENSEC3) != 0) {
dns_qpmulti_query(qpdb->nsec3, &search.qpr);