/*
* __wt_page_in_func --
* Acquire a hazard pointer to a page; if the page is not in-memory,
* read it from the disk and build an in-memory version.
*/
int
__wt_page_in_func(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t flags
#ifdef HAVE_DIAGNOSTIC
, const char *file, int line
#endif
)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_PAGE *page;
u_int sleep_cnt, wait_cnt;
int busy, cache_work, force_attempts, oldgen, stalled;
btree = S2BT(session);
stalled = 0;
for (force_attempts = oldgen = 0, sleep_cnt = wait_cnt = 0;;) {
switch (ref->state) {
case WT_REF_DISK:
case WT_REF_DELETED:
if (LF_ISSET(WT_READ_CACHE))
return (WT_NOTFOUND);
/*
* The page isn't in memory, read it. If this thread is
* allowed to do eviction work, check for space in the
* cache.
*/
if (!LF_ISSET(WT_READ_NO_EVICT))
WT_RET(__wt_cache_eviction_check(
session, 1, NULL));
WT_RET(__page_read(session, ref));
oldgen = LF_ISSET(WT_READ_WONT_NEED) ||
F_ISSET(session, WT_SESSION_NO_CACHE);
continue;
case WT_REF_READING:
if (LF_ISSET(WT_READ_CACHE))
return (WT_NOTFOUND);
if (LF_ISSET(WT_READ_NO_WAIT))
return (WT_NOTFOUND);
/* Waiting on another thread's read, stall. */
WT_STAT_FAST_CONN_INCR(session, page_read_blocked);
stalled = 1;
break;
case WT_REF_LOCKED:
if (LF_ISSET(WT_READ_NO_WAIT))
return (WT_NOTFOUND);
/* Waiting on eviction, stall. */
WT_STAT_FAST_CONN_INCR(session, page_locked_blocked);
stalled = 1;
break;
case WT_REF_SPLIT:
return (WT_RESTART);
case WT_REF_MEM:
/*
* The page is in memory.
*
* Get a hazard pointer if one is required. We cannot
* be evicting if no hazard pointer is required, we're
* done.
*/
if (F_ISSET(btree, WT_BTREE_IN_MEMORY))
goto skip_evict;
/*
* The expected reason we can't get a hazard pointer is
* because the page is being evicted, yield, try again.
*/
#ifdef HAVE_DIAGNOSTIC
WT_RET(
__wt_hazard_set(session, ref, &busy, file, line));
#else
WT_RET(__wt_hazard_set(session, ref, &busy));
#endif
if (busy) {
WT_STAT_FAST_CONN_INCR(
session, page_busy_blocked);
break;
}
/*
* If eviction is configured for this file, check to see
* if the page qualifies for forced eviction and update
* the page's generation number. If eviction isn't being
* done on this file, we're done.
*/
if (LF_ISSET(WT_READ_NO_EVICT) ||
F_ISSET(session, WT_SESSION_NO_EVICTION) ||
F_ISSET(btree, WT_BTREE_NO_EVICTION))
goto skip_evict;
/*
* Forcibly evict pages that are too big.
*/
page = ref->page;
if (force_attempts < 10 &&
__evict_force_check(session, page)) {
++force_attempts;
ret = __wt_page_release_evict(session, ref);
/* If forced eviction fails, stall. */
if (ret == EBUSY) {
ret = 0;
WT_STAT_FAST_CONN_INCR(session,
page_forcible_evict_blocked);
stalled = 1;
break;
}
WT_RET(ret);
/*
* The result of a successful forced eviction
* is a page-state transition (potentially to
* an in-memory page we can use, or a restart
* return for our caller), continue the outer
* page-acquisition loop.
*/
continue;
}
/*
* If we read the page and we are configured to not
* trash the cache, set the oldest read generation so
* the page is forcibly evicted as soon as possible.
*
* Otherwise, update the page's read generation.
*/
if (oldgen && page->read_gen == WT_READGEN_NOTSET)
__wt_page_evict_soon(page);
else if (!LF_ISSET(WT_READ_NO_GEN) &&
page->read_gen != WT_READGEN_OLDEST &&
page->read_gen < __wt_cache_read_gen(session))
page->read_gen =
__wt_cache_read_gen_bump(session);
skip_evict:
/*
* Check if we need an autocommit transaction.
* Starting a transaction can trigger eviction, so skip
* it if eviction isn't permitted.
*/
return (LF_ISSET(WT_READ_NO_EVICT) ? 0 :
__wt_txn_autocommit_check(session));
WT_ILLEGAL_VALUE(session);
}
/*
* We failed to get the page -- yield before retrying, and if
* we've yielded enough times, start sleeping so we don't burn
* CPU to no purpose.
*/
if (stalled)
wait_cnt += 1000;
else if (++wait_cnt < 1000) {
__wt_yield();
continue;
}
/*
* If stalling and this thread is allowed to do eviction work,
* check if the cache needs help. If we do work for the cache,
* substitute that for a sleep.
*/
if (!LF_ISSET(WT_READ_NO_EVICT)) {
WT_RET(
__wt_cache_eviction_check(session, 1, &cache_work));
if (cache_work)
continue;
}
sleep_cnt = WT_MIN(sleep_cnt + 1000, 10000);
WT_STAT_FAST_CONN_INCRV(session, page_sleep, sleep_cnt);
__wt_sleep(0, sleep_cnt);
}
}
/*
* __wt_page_in_func --
* Acquire a hazard pointer to a page; if the page is not in-memory,
* read it from the disk and build an in-memory version.
*/
int
__wt_page_in_func(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t flags
#ifdef HAVE_DIAGNOSTIC
, const char *file, int line
#endif
)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_PAGE *page;
u_int sleep_cnt, wait_cnt;
bool busy, cache_work, evict_soon, stalled;
int force_attempts;
btree = S2BT(session);
/*
* Ignore reads of pages already known to be in cache, otherwise the
* eviction server can dominate these statistics.
*/
if (!LF_ISSET(WT_READ_CACHE)) {
WT_STAT_FAST_CONN_INCR(session, cache_pages_requested);
WT_STAT_FAST_DATA_INCR(session, cache_pages_requested);
}
for (evict_soon = stalled = false,
force_attempts = 0, sleep_cnt = wait_cnt = 0;;) {
switch (ref->state) {
case WT_REF_DELETED:
if (LF_ISSET(WT_READ_NO_EMPTY) &&
__wt_delete_page_skip(session, ref, false))
return (WT_NOTFOUND);
/* FALLTHROUGH */
case WT_REF_DISK:
if (LF_ISSET(WT_READ_CACHE))
return (WT_NOTFOUND);
/*
* The page isn't in memory, read it. If this thread is
* allowed to do eviction work, check for space in the
* cache.
*/
if (!LF_ISSET(WT_READ_NO_EVICT))
WT_RET(__wt_cache_eviction_check(
session, 1, NULL));
WT_RET(__page_read(session, ref));
/*
* If configured to not trash the cache, leave the page
* generation unset, we'll set it before returning to
* the oldest read generation, so the page is forcibly
* evicted as soon as possible. We don't do that set
* here because we don't want to evict the page before
* we "acquire" it.
*/
evict_soon = LF_ISSET(WT_READ_WONT_NEED) ||
F_ISSET(session, WT_SESSION_NO_CACHE);
continue;
case WT_REF_READING:
if (LF_ISSET(WT_READ_CACHE))
return (WT_NOTFOUND);
if (LF_ISSET(WT_READ_NO_WAIT))
return (WT_NOTFOUND);
/* Waiting on another thread's read, stall. */
WT_STAT_FAST_CONN_INCR(session, page_read_blocked);
stalled = true;
break;
case WT_REF_LOCKED:
if (LF_ISSET(WT_READ_NO_WAIT))
return (WT_NOTFOUND);
/* Waiting on eviction, stall. */
WT_STAT_FAST_CONN_INCR(session, page_locked_blocked);
stalled = true;
break;
case WT_REF_SPLIT:
return (WT_RESTART);
case WT_REF_MEM:
/*
* The page is in memory.
*
* Get a hazard pointer if one is required. We cannot
* be evicting if no hazard pointer is required, we're
* done.
*/
if (F_ISSET(btree, WT_BTREE_IN_MEMORY))
goto skip_evict;
/*
* The expected reason we can't get a hazard pointer is
* because the page is being evicted, yield, try again.
*/
#ifdef HAVE_DIAGNOSTIC
WT_RET(
__wt_hazard_set(session, ref, &busy, file, line));
#else
WT_RET(__wt_hazard_set(session, ref, &busy));
#endif
if (busy) {
WT_STAT_FAST_CONN_INCR(
session, page_busy_blocked);
break;
}
/*
* If eviction is configured for this file, check to see
* if the page qualifies for forced eviction and update
* the page's generation number. If eviction isn't being
* done on this file, we're done.
* In-memory split of large pages is allowed while
* no_eviction is set on btree, whereas reconciliation
* is not allowed.
*/
if (LF_ISSET(WT_READ_NO_EVICT) ||
F_ISSET(session, WT_SESSION_NO_EVICTION) ||
(F_ISSET(btree, WT_BTREE_NO_EVICTION) &&
!F_ISSET(btree, WT_BTREE_NO_RECONCILE)))
goto skip_evict;
/*
* Forcibly evict pages that are too big.
*/
if (force_attempts < 10 &&
__evict_force_check(session, ref)) {
++force_attempts;
ret = __wt_page_release_evict(session, ref);
/* If forced eviction fails, stall. */
if (ret == EBUSY) {
ret = 0;
WT_STAT_FAST_CONN_INCR(session,
page_forcible_evict_blocked);
stalled = true;
break;
}
WT_RET(ret);
/*
* The result of a successful forced eviction
* is a page-state transition (potentially to
* an in-memory page we can use, or a restart
* return for our caller), continue the outer
* page-acquisition loop.
*/
continue;
}
/*
* If we read the page and are configured to not trash
* the cache, and no other thread has already used the
* page, set the oldest read generation so the page is
* forcibly evicted as soon as possible.
*
* Otherwise, if we read the page, or, if configured to
* update the page's read generation and the page isn't
* already flagged for forced eviction, update the page
* read generation.
*/
page = ref->page;
if (page->read_gen == WT_READGEN_NOTSET) {
if (evict_soon)
__wt_page_evict_soon(session, ref);
else
__wt_cache_read_gen_new(session, page);
} else if (!LF_ISSET(WT_READ_NO_GEN))
__wt_cache_read_gen_bump(session, page);
skip_evict:
/*
* Check if we need an autocommit transaction.
* Starting a transaction can trigger eviction, so skip
* it if eviction isn't permitted.
*/
return (LF_ISSET(WT_READ_NO_EVICT) ? 0 :
__wt_txn_autocommit_check(session));
WT_ILLEGAL_VALUE(session);
}
/*
* We failed to get the page -- yield before retrying, and if
* we've yielded enough times, start sleeping so we don't burn
* CPU to no purpose.
*/
if (stalled)
wait_cnt += WT_THOUSAND;
else if (++wait_cnt < WT_THOUSAND) {
__wt_yield();
continue;
}
/*
* If stalling and this thread is allowed to do eviction work,
* check if the cache needs help. If we do work for the cache,
* substitute that for a sleep.
*/
if (!LF_ISSET(WT_READ_NO_EVICT)) {
WT_RET(
__wt_cache_eviction_check(session, 1, &cache_work));
if (cache_work)
continue;
}
sleep_cnt = WT_MIN(sleep_cnt + WT_THOUSAND, 10000);
WT_STAT_FAST_CONN_INCRV(session, page_sleep, sleep_cnt);
__wt_sleep(0, sleep_cnt);
}
}
