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Merge branch '4591-improve-ttl-based-cleaning' into 'main'

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Remove expired rdataset headers from the heap

Closes #4591

See merge request isc-projects/bind9!8754
This commit is contained in:
Ondřej Surý 2024-02-29 12:33:58 +00:00
commit 7111ea3669
2 changed files with 63 additions and 10 deletions
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5
CHANGES
View file

@ -1,3 +1,8 @@
6353. [bug] Improve the TTL-based cleaning by removing the expired
headers from the heap, so they don't block the next
cleaning round and clean more than a single item for
each new addition to the RBTDB. [GL #4591]
6352. [bug] Revert change 6319 and decrease lock contention during
RBTDB tree pruning by not cleaning up nodes recursively
within a single prune_tree() call. [GL #4596]

68
lib/dns/rbtdb.c
View file

@ -154,6 +154,14 @@
#define DEFAULT_CACHE_NODE_LOCK_COUNT 17
#endif /* DNS_RBTDB_CACHE_NODE_LOCK_COUNT */
/*
* This defines the number of headers that we try to expire each time the
* expire_ttl_headers() is run. The number should be small enough, so the
* TTL-based header expiration doesn't take too long, but it should be large
* enough, so we expire enough headers if their TTL is clustered.
*/
#define DNS_RBTDB_EXPIRE_TTL_COUNT 10
static void
delete_callback(void *data, void *arg);
static void
@ -337,6 +345,10 @@ dns__rbtdb_setttl(dns_slabheader_t *header, dns_ttl_t newttl) {
} else {
isc_heap_decreased(header->heap, header->heap_index);
}
if (newttl == 0) {
isc_heap_delete(header->heap, header->heap_index);
}
}
static bool
@ -3160,6 +3172,11 @@ cleanup:
return (result);
}
static void
expire_ttl_headers(dns_rbtdb_t *rbtdb, unsigned int locknum,
isc_rwlocktype_t *tlocktypep, isc_stdtime_t now,
bool cache_is_overmem DNS__DB_FLARG);
isc_result_t
dns__rbtdb_addrdataset(dns_db_t *db, dns_dbnode_t *node,
dns_dbversion_t *version, isc_stdtime_t now,
@ -3170,7 +3187,6 @@ dns__rbtdb_addrdataset(dns_db_t *db, dns_dbnode_t *node,
dns_rbtdb_version_t *rbtversion = version;
isc_region_t region;
dns_slabheader_t *newheader = NULL;
dns_slabheader_t *header = NULL;
isc_result_t result;
bool delegating;
bool newnsec;
@ -3342,14 +3358,8 @@ dns__rbtdb_addrdataset(dns_db_t *db, dns_dbnode_t *node,
rbtnode->locknum DNS__DB_FLARG_PASS);
}
header = isc_heap_element(rbtdb->heaps[rbtnode->locknum], 1);
if (header != NULL && header->ttl + STALE_TTL(header, rbtdb) <
now - RBTDB_VIRTUAL)
{
dns__cacherbt_expireheader(
header, &tlocktype,
dns_expire_ttl DNS__DB_FLARG_PASS);
}
expire_ttl_headers(rbtdb, rbtnode->locknum, &tlocktype, now,
cache_is_overmem DNS__DB_FLARG_PASS);
/*
* If we've been holding a write lock on the tree just for
@ -4851,7 +4861,6 @@ dns__rbtdb_deletedata(dns_db_t *db ISC_ATTR_UNUSED,
if (header->heap != NULL && header->heap_index != 0) {
isc_heap_delete(header->heap, header->heap_index);
}
header->heap_index = 0;
if (IS_CACHE(rbtdb)) {
update_rrsetstats(rbtdb->rrsetstats, header->type,
@ -4876,3 +4885,42 @@ dns__rbtdb_deletedata(dns_db_t *db ISC_ATTR_UNUSED,
}
}
}
/*
* Caller must be holding the node write lock.
*/
static void
expire_ttl_headers(dns_rbtdb_t *rbtdb, unsigned int locknum,
isc_rwlocktype_t *tlocktypep, isc_stdtime_t now,
bool cache_is_overmem DNS__DB_FLARG) {
isc_heap_t *heap = rbtdb->heaps[locknum];
for (size_t i = 0; i < DNS_RBTDB_EXPIRE_TTL_COUNT; i++) {
dns_slabheader_t *header = isc_heap_element(heap, 1);
if (header == NULL) {
/* No headers left on this TTL heap; exit cleaning */
return;
}
dns_ttl_t ttl = header->ttl;
if (!cache_is_overmem) {
/* Only account for stale TTL if cache is not overmem */
ttl += STALE_TTL(header, rbtdb);
}
if (ttl >= now - RBTDB_VIRTUAL) {
/*
* The header at the top of this TTL heap is not yet
* eligible for expiry, so none of the other headers on
* the same heap can be eligible for expiry, either;
* exit cleaning.
*/
return;
}
dns__cacherbt_expireheader(header, tlocktypep,
dns_expire_ttl DNS__DB_FLARG_PASS);
}
}