Skip to content

Commit

Permalink
reorg juggle routine, replace prints with stats
Browse files Browse the repository at this point in the history 
code is clearer, and able to react a bit faster to required evictions.
  • Loading branch information
@dormando
dormando committed Jan 5, 2015
1 parent fb26989 commit f7bf26c
Show file tree
Hide file tree
Showing 2 changed files with 47 additions and 37 deletions.
82 changes: 45 additions & 37 deletions items.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,17 @@ static void item_unlink_q(item *it);
typedef struct {
uint64_t evicted;
uint64_t evicted_nonzero;
rel_time_t evicted_time;
uint64_t reclaimed;
uint64_t outofmemory;
uint64_t tailrepairs;
uint64_t expired_unfetched;
uint64_t evicted_unfetched;
uint64_t crawler_reclaimed;
uint64_t lrutail_reflocked;
uint64_t moves_to_cold;
uint64_t moves_to_warm;
uint64_t moves_within_lru;
rel_time_t evicted_time;
} itemstats_t;

static item *heads[LARGEST_ID];
Expand Down Expand Up @@ -579,6 +582,9 @@ void item_stats_totals(ADD_STAT add_stats, void *c) {
totals.reclaimed += itemstats[i].reclaimed;
totals.crawler_reclaimed += itemstats[i].crawler_reclaimed;
totals.lrutail_reflocked += itemstats[i].lrutail_reflocked;
totals.moves_to_cold += itemstats[i].moves_to_cold;
totals.moves_to_warm += itemstats[i].moves_to_warm;
totals.moves_within_lru += itemstats[i].moves_within_lru;
pthread_mutex_unlock(&lru_locks[i]);
}
APPEND_STAT("expired_unfetched", "%llu",
Expand All @@ -593,6 +599,12 @@ void item_stats_totals(ADD_STAT add_stats, void *c) {
(unsigned long long)totals.crawler_reclaimed);
APPEND_STAT("lrutail_reflocked", "%llu",
(unsigned long long)totals.lrutail_reflocked);
APPEND_STAT("moves_to_cold", "%llu",
(unsigned long long)totals.moves_to_cold);
APPEND_STAT("moves_to_warm", "%llu",
(unsigned long long)totals.moves_to_warm);
APPEND_STAT("moves_within_lru", "%llu",
(unsigned long long)totals.moves_within_lru);
}

void item_stats(ADD_STAT add_stats, void *c) {
Expand Down Expand Up @@ -630,6 +642,12 @@ void item_stats(ADD_STAT add_stats, void *c) {
"%llu", (unsigned long long)itemstats[i].crawler_reclaimed);
APPEND_NUM_FMT_STAT(fmt, i, "lrutail_reflocked",
"%llu", (unsigned long long)itemstats[i].lrutail_reflocked);
APPEND_NUM_FMT_STAT(fmt, i, "moves_to_cold",
"%llu", (unsigned long long)itemstats[i].moves_to_cold);
APPEND_NUM_FMT_STAT(fmt, i, "moves_to_warm",
"%llu", (unsigned long long)itemstats[i].moves_to_warm);
APPEND_NUM_FMT_STAT(fmt, i, "moves_within_lru",
"%llu", (unsigned long long)itemstats[i].moves_within_lru);
}
pthread_mutex_unlock(&lru_locks[i]);
}
Expand Down Expand Up @@ -761,21 +779,14 @@ item *do_item_touch(const char *key, size_t nkey, uint32_t exptime,
/*** LRU MAINTENANCE THREAD ***/

/* Returns number of items remove, expired, or evicted */
/* FIXME: I *think* since we're always intending to pop an item from the
* bottom of cold, we only need to hold the cold LRU lock long enough to
* iten_lock something valid. Then we remove the lock, and can fiddle with the
* item. However, do_item_unlink_nolock() will need an option for "skip the
* LRU removal"
*/
static int lru_pull_tail(const int orig_id, const int cur_lru,
const unsigned int total_chunks, const bool do_evict) {
const unsigned int total_chunks, const bool do_evict, const uint32_t cur_hv) {
item *it = NULL;
int id = orig_id;
int removed = 0;
if (id == 0)
return 0;

/* do a quick check if we have any expired items in the tail.. */
int tries = 5;
item *search;
item *next_it;
Expand All @@ -798,10 +809,9 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,
}
uint32_t hv = hash(ITEM_key(search), search->nkey);
/* Attempt to hash item lock the "search" item. If locked, no
* other callers can incr the refcount
* other callers can incr the refcount. Also skip ourselves.
*/
/* Don't accidentally grab ourselves, or bail if we can't quicklock */
if ((hold_lock = item_trylock(hv)) == NULL)
if (hv == cur_hv || (hold_lock = item_trylock(hv)) == NULL)
continue;
/* Now see if the item is refcount locked */
if (refcount_incr(&search->refcount) != 2) {
Expand Down Expand Up @@ -843,22 +853,21 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,
* If we're COLD_LRU, send to WARM_LRU unless we need to evict
*/
/* FIXME: Hardcoded percentage */
/* FIXME: Won't aggressively pull from cold into warm */
switch (cur_lru) {
case HOT_LRU:
limit = total_chunks * 32 / 100;
case WARM_LRU:
limit = total_chunks * 32 / 100;
if (sizes[id] > limit) {
/* FIXME: Counter for move-to-cold */
itemstats[id].moves_to_cold++;
move_to_lru = COLD_LRU;
do_item_unlink_q(search);
it = search;
removed++;
break;
} else if ((search->it_flags & ITEM_ACTIVE) != 0) {
/* Only allow ACTIVE relinking if we're not too large. */
fprintf(stderr, "doing item update from %d\n", orig_id);
itemstats[id].moves_within_lru++;
search->it_flags &= ~ITEM_ACTIVE;
do_item_update_nolock(search);
do_item_remove(search);
Expand All @@ -872,8 +881,7 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,
it = search; /* No matter what, we're stopping */
if (do_evict) {
if (settings.evict_to_free == 0) {
/* FIXME: New counter that means "tried to evict" */
itemstats[id].outofmemory++;
/* Don't think we need a counter for this. It'll OOM. */
break;
}
itemstats[id].evicted++;
Expand All @@ -886,6 +894,7 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,
do_item_unlink_nolock(it, hv);
removed++;
} else if ((search->it_flags & ITEM_ACTIVE) != 0) {
itemstats[id].moves_to_warm++;
search->it_flags &= ~ITEM_ACTIVE;
move_to_lru = WARM_LRU;
do_item_unlink_q(search);
Expand All @@ -901,11 +910,8 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,

if (it != NULL) {
if (move_to_lru) {
fprintf(stderr, "moving from [%d]_lru to [%d]_lru\n", cur_lru, move_to_lru);
it->slabs_clsid &= ~(3>>6);
fprintf(stderr, "- removed cur_lru %d\n", it->slabs_clsid);
it->slabs_clsid |= move_to_lru;
fprintf(stderr, "- added [%d]_lru %d\n", move_to_lru, it->slabs_clsid);
item_link_q(it);
}
do_item_remove(it);
Expand All @@ -927,25 +933,26 @@ static void lru_maintainer_juggle(const int slabs_clsid) {
unsigned int total_chunks = 0;
unsigned int free_chunks = slabs_available_chunks(slabs_clsid,
&mem_limit_reached, &total_chunks);
//fprintf(stderr, "really starting LRU juggle\n");
STATS_LOCK();
stats.lru_maintainer_juggles++;
STATS_UNLOCK();

/* Juggle HOT/WARM up to N times */
for (i = 0; i < 50; i++) {
if (!lru_pull_tail(slabs_clsid, HOT_LRU, total_chunks, false) &&
!lru_pull_tail(slabs_clsid, WARM_LRU, total_chunks, false)) {
break;
int do_more = 0;
int removed = 0;
if (lru_pull_tail(slabs_clsid, HOT_LRU, total_chunks, false, 0) &&
lru_pull_tail(slabs_clsid, WARM_LRU, total_chunks, false, 0)) {
do_more++;
}
}

/* Less than high watermark */
/* If less than low watermark and no more pages available, evict */
/* FIXME: More tries if it shuffled .... something? */
for (i = 0; i < 50 && free_chunks < 100; i++) {
int removed = lru_pull_tail(slabs_clsid, COLD_LRU, total_chunks,
(free_chunks < 50 && mem_limit_reached) ? true : false);
if (removed == 0)
break;
/* FIXME: evictions under low watermark is hardcoded */
removed = lru_pull_tail(slabs_clsid, COLD_LRU, total_chunks,
(free_chunks < 50 && mem_limit_reached) ? true : false, 0);
if (removed != 0)
do_more++;
free_chunks += removed;
if (do_more == 0)
break;
}
}

Expand All @@ -965,7 +972,8 @@ static void *lru_maintainer_thread(void *arg) {
ts.tv_sec = tv.tv_sec + 1;
pthread_cond_timedwait(&lru_maintainer_cond, &lru_maintainer_lock, &ts);

fprintf(stderr, "LRU maintainer thread running\n");
if (verbose > 2)
fprintf(stderr, "LRU maintainer thread running\n");
/* We were asked to immediately wake up and poke a particular slab
* class due to a low watermark being hit */
if (lru_maintainer_check_clsid != 0) {
Expand Down Expand Up @@ -996,7 +1004,7 @@ int stop_lru_maintainer_thread(void) {
fprintf(stderr, "Failed to stop LRU maintainer thread: %s\n", strerror(ret));
return -1;
}
//settings.lru_maintainer_thread = false;
settings.lru_maintainer_thread = false;
return 0;
}

Expand All @@ -1005,7 +1013,7 @@ int start_lru_maintainer_thread(void) {

pthread_mutex_lock(&lru_maintainer_lock);
do_run_lru_maintainer_thread = 1;
//settings.lru_maintainer_thread = true;
settings.lru_maintainer_thread = true;
if ((ret = pthread_create(&lru_maintainer_tid, NULL,
lru_maintainer_thread, NULL)) != 0) {
fprintf(stderr, "Can't create LRU maintainer thread: %s\n",
Expand Down
2 changes: 2 additions & 0 deletions memcached.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -286,6 +286,7 @@ struct stats {
bool slab_reassign_running; /* slab reassign in progress */
uint64_t slabs_moved; /* times slabs were moved around */
bool lru_crawler_running; /* crawl in progress */
uint64_t lru_maintainer_juggles; /* number of LRU bg pokes */
};

#define MAX_VERBOSITY_LEVEL 2
Expand Down Expand Up @@ -321,6 +322,7 @@ struct settings {
bool sasl; /* SASL on/off */
bool maxconns_fast; /* Whether or not to early close connections */
bool lru_crawler; /* Whether or not to enable the autocrawler thread */
bool lru_maintainer_thread; /* LRU maintainer background thread */
bool slab_reassign; /* Whether or not slab reassignment is allowed */
int slab_automove; /* Whether or not to automatically move slabs */
int hashpower_init; /* Starting hash power level */
Expand Down

0 comments on commit f7bf26c

Please sign in to comment.