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Try to skip lock on fully lower names

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If the name is fully lowercase, we don't need to access the case bitmap
in order to set the case. Therefore, we can check for the FULLYLOWERCASE
flag using only atomic operations, and skip a lock in the hot path,
provided we clear the FULLYLOWERCASE flag before changing the case
bitmap.
This commit is contained in:
Alessio Podda 2025-05-28 14:33:04 +02:00 committed by Ondřej Surý
parent b814434836
commit 4a6d7eb4f3
1 changed files with 8 additions and 10 deletions
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18
lib/dns/rdataslab.c
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@ -870,7 +870,7 @@ dns_slabheader_reset(dns_slabheader_t *h, dns_db_t *db, dns_dbnode_t *node) {
atomic_init(&h->attributes, 0);
atomic_init(&h->last_refresh_fail_ts, 0);
STATIC_ASSERT((sizeof(h->attributes) == 2),
STATIC_ASSERT(sizeof(h->attributes) == 2,
"The .attributes field of dns_slabheader_t needs to be "
"16-bit int type exactly.");
}
@ -1208,6 +1208,8 @@ static void
rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name) {
dns_slabheader_t *header = dns_rdataset_getheader(rdataset);
DNS_SLABHEADER_CLRATTR(header, DNS_SLABHEADERATTR_CASEFULLYLOWER);
dns_db_locknode(header->db, header->node, isc_rwlocktype_write);
dns_slabheader_setownercase(header, name);
dns_db_unlocknode(header->db, header->node, isc_rwlocktype_write);
@ -1219,15 +1221,13 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
uint8_t mask = (1 << 7);
uint8_t bits = 0;
dns_db_locknode(header->db, header->node, isc_rwlocktype_read);
if (!CASESET(header)) {
goto unlock;
}
if (CASEFULLYLOWER(header)) {
isc_ascii_lowercopy(name->ndata, name->ndata, name->length);
} else {
return;
}
dns_db_locknode(header->db, header->node, isc_rwlocktype_read);
if (CASESET(header)) {
uint8_t *nd = name->ndata;
for (size_t i = 0; i < name->length; i++) {
if (mask == (1 << 7)) {
@ -1240,8 +1240,6 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
: isc_ascii_tolower(nd[i]);
}
}
unlock:
dns_db_unlocknode(header->db, header->node, isc_rwlocktype_read);
}