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proc-cache.c: lazy delete

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Use lazy delete mechanism to remove the need for linked list delete.
This removes the need for a sentinel node at the beginning.
This commit is contained in:
Henrik Hautakoski 2012-07-04 12:02:42 +02:00
parent 51f7286ab8
commit ae91737fb1
1 changed files with 26 additions and 29 deletions
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55
proc-cache.c
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@ -48,6 +48,9 @@ union hash {
unsigned char sha1[20]; unsigned char sha1[20];
}; };
/* hash entry flags */
#define HE_FLAG_VALID (1 << 0)
/* /*
* NOTE: be sure to change this constant if the struct's size changes. * NOTE: be sure to change this constant if the struct's size changes.
*/ */
@ -55,9 +58,12 @@ union hash {
struct proc_cache_entry { struct proc_cache_entry {
union hash hash; union hash hash;
unsigned int time; unsigned int time;
unsigned int flags;
struct llist list; struct llist list;
}; };
#define he_empty(x) (!(x) || !((x)->flags & HE_FLAG_VALID))
static struct lockfile lock = LOCKFILE_INIT; static struct lockfile lock = LOCKFILE_INIT;
static struct hash_table table = HASH_TABLE_INIT; static struct hash_table table = HASH_TABLE_INIT;
@ -93,7 +99,7 @@ static struct proc_cache_entry* lookup(const char *key) {
llist_foreach(it, entry->list.next) { llist_foreach(it, entry->list.next) {
e = llist_entry(it, struct proc_cache_entry, list); e = llist_entry(it, struct proc_cache_entry, list);
if (!memcmp(e->hash.sha1, h.sha1, 20)) if (!he_empty(e) && !memcmp(e->hash.sha1, h.sha1, 20))
return e; return e;
} }
} }
@ -102,32 +108,26 @@ static struct proc_cache_entry* lookup(const char *key) {
static void he_insert(struct proc_cache_entry *entry) { static void he_insert(struct proc_cache_entry *entry) {
struct proc_cache_entry *dest, *s; struct proc_cache_entry *dest;
s = calloc(1, sizeof(*s)); dest = hash_insert(&table, entry->hash.index, entry);
dest = hash_insert(&table, entry->hash.index, s);
if (dest) { if (dest) {
struct llist *it; struct llist *it;
struct proc_cache_entry *e; struct proc_cache_entry *e;
free(s); llist_foreach(it, &dest->list) {
llist_foreach(it, dest->list.next) {
e = llist_entry(it, struct proc_cache_entry, list); e = llist_entry(it, struct proc_cache_entry, list);
if (!memcmp(entry->hash.sha1, e->hash.sha1, 20)) { if (!he_empty(e) &&
!memcmp(e->hash.sha1, entry->hash.sha1, 20)) {
free(entry); free(entry);
return; return;
} }
} }
llist_add(&dest->list, &entry->list); llist_add(&dest->list, &entry->list);
} else {
s->hash.index = entry->hash.index;
llist_add(&s->list, &entry->list);
} }
entry->flags |= HE_FLAG_VALID;
} }
static void build_table(const char *buf, size_t entries) { static void build_table(const char *buf, size_t entries) {
@ -240,24 +240,16 @@ void proc_cache_purge(unsigned int timestamp) {
t = now - timestamp; t = now - timestamp;
for(i=0; i < table.size; i++) { for(i=0; i < table.size; i++) {
struct llist *it, *n; struct llist *it;
struct proc_cache_entry *e, *entry = hash_entry(&table, i); struct proc_cache_entry *e, *entry = hash_entry(&table, i);
if (!entry) if (!entry)
continue; continue;
llist_foreach_safe(it, n, entry->list.next) { llist_foreach(it, &entry->list) {
e = llist_entry(it, struct proc_cache_entry, list); e = llist_entry(it, struct proc_cache_entry, list);
if (e->time <= t) { if (!he_empty(e) && e->time <= t)
llist_del(&entry->list, it); e->flags &= ~HE_FLAG_VALID;
free(e);
}
}
if (llist_empty(&entry->list)) {
e = hash_remove(&table, entry->hash.index);
if (e)
free(e);
} }
} }
} }
@ -298,9 +290,14 @@ void proc_cache_close() {
if (!entry) if (!entry)
continue; continue;
llist_foreach(it, entry->list.next) { llist_foreach(it, &entry->list) {
write_entry(fd, llist_entry(it, struct proc_cache_entry, list)); struct proc_cache_entry *e;
hdr.entries++;
e = llist_entry(it, struct proc_cache_entry, list);
if (!he_empty(e)) {
write_entry(fd, e);
hdr.entries++;
}
} }
} }