/*
* __wt_compact --
* Compact a file.
*/
int
__wt_compact(WT_SESSION_IMPL *session, const char *cfg[])
{
WT_BM *bm;
WT_CONFIG_ITEM cval;
WT_DECL_RET;
WT_PAGE *page;
int trigger, skip;
bm = S2BT(session)->bm;
WT_DSTAT_INCR(session, session_compact);
WT_RET(__wt_config_gets(session, cfg, "trigger", &cval));
trigger = (int)cval.val;
/* Check if compaction might be useful. */
WT_RET(bm->compact_skip(bm, session, trigger, &skip));
if (skip)
return (0);
/*
* Walk the cache reviewing in-memory pages to see if they need to be
* re-written. This requires looking at page reconciliation results,
* which means the page cannot be reconciled at the same time as it's
* being reviewed for compaction. The underlying functions ensure we
* don't collide with page eviction, but we need to make sure we don't
* collide with checkpoints either, they are the other operation that
* can reconcile a page.
*/
__wt_spin_lock(session, &S2C(session)->metadata_lock);
WT_RET(__wt_bt_cache_op(session, NULL, WT_SYNC_COMPACT));
__wt_spin_unlock(session, &S2C(session)->metadata_lock);
/*
* Walk the tree, reviewing on-disk pages to see if they need to be
* re-written.
*/
for (page = NULL;;) {
WT_RET(__wt_tree_walk(session, &page, WT_TREE_COMPACT));
if (page == NULL)
break;
/*
* The only pages returned by the tree walk function are pages
* we want to re-write; mark the page and tree dirty.
*/
if ((ret = __wt_page_modify_init(session, page)) != 0) {
WT_TRET(__wt_page_release(session, page));
WT_RET(ret);
}
__wt_page_and_tree_modify_set(session, page);
WT_DSTAT_INCR(session, btree_compact_rewrite);
}
return (0);
}
/*
* __wt_btcur_next_random --
* Move to a random record in the tree.
*/
int
__wt_btcur_next_random(WT_CURSOR_BTREE *cbt)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)cbt->iface.session;
btree = cbt->btree;
WT_DSTAT_INCR(session, cursor_next);
retry: WT_RET(__cursor_func_init(cbt, 1));
__cursor_position_clear(cbt);
/*
* Only supports row-store: applications can trivially select a random
* value from a column-store, if there were any reason to do so.
*/
WT_ERR(btree->type == BTREE_ROW ?
__wt_row_random(session, cbt) : ENOTSUP);
ret = cbt->compare == 0 ?
__wt_kv_return(session, cbt) : WT_NOTFOUND;
err: if (ret == WT_RESTART)
goto retry;
WT_TRET(__cursor_func_resolve(cbt, ret));
return (ret);
}
/*
* __hazard_exclusive --
* Request exclusive access to a page.
*/
static int
__hazard_exclusive(WT_SESSION_IMPL *session, WT_REF *ref, int top)
{
/*
* Make sure there is space to track exclusive access so we can unlock
* to clean up.
*/
if (session->excl_next * sizeof(WT_REF *) == session->excl_allocated)
WT_RET(__wt_realloc(session, &session->excl_allocated,
(session->excl_next + 50) * sizeof(WT_REF *),
&session->excl));
/*
* Hazard pointers are acquired down the tree, which means we can't
* deadlock.
*
* Request exclusive access to the page. The top-level page should
* already be in the locked state, lock child pages in memory.
* If another thread already has this page, give up.
*/
if (!top && !WT_ATOMIC_CAS(ref->state, WT_REF_MEM, WT_REF_LOCKED))
return (EBUSY); /* We couldn't change the state. */
WT_ASSERT(session, ref->state == WT_REF_LOCKED);
session->excl[session->excl_next++] = ref;
/* Check for a matching hazard pointer. */
if (__wt_page_hazard_check(session, ref->page) == NULL)
return (0);
WT_DSTAT_INCR(session, cache_eviction_hazard);
WT_CSTAT_INCR(session, cache_eviction_hazard);
WT_VERBOSE_RET(
session, evict, "page %p hazard request failed", ref->page);
return (EBUSY);
}
/*
* __wt_merge_tree --
* Attempt to collapse a stack of split-merge pages in memory into a
* shallow tree. If enough keys are found, create a real internal node
* that can be evicted (and, if necessary, split further).
*
* This code is designed to deal with workloads that otherwise create
* arbitrarily deep (and slow) trees in memory.
*/
int
__wt_merge_tree(WT_SESSION_IMPL *session, WT_PAGE *top)
{
WT_DECL_RET;
WT_PAGE *lchild, *newtop, *rchild;
WT_REF *newref;
WT_VISIT_STATE visit_state;
uint32_t refcnt, split;
int promote;
u_int levels;
uint8_t page_type;
WT_CLEAR(visit_state);
visit_state.session = session;
lchild = newtop = rchild = NULL;
page_type = top->type;
WT_ASSERT(session, __wt_btree_mergeable(top));
WT_ASSERT(session, top->ref->state == WT_REF_LOCKED);
/*
* Walk the subtree, count the references at the bottom level and
* calculate the maximum depth.
*/
WT_RET(__merge_walk(session, top, 1, __merge_count, &visit_state));
/* If there aren't enough useful levels, give up. */
if (visit_state.maxdepth < WT_MERGE_STACK_MIN)
return (EBUSY);
/*
* Don't allow split merges to generate arbitrarily large pages.
* Ideally we would choose a size based on the internal_page_max
* setting for the btree, but we don't have the correct btree handle
* available.
*/
if (visit_state.refcnt > WT_MERGE_MAX_REFS)
return (EBUSY);
/*
* Now we either collapse the internal pages into one split-merge page,
* or if there are "enough" keys, we split into two equal internal
* pages, each of which can be evicted independently.
*
* We set a flag (WT_PM_REC_SPLIT_MERGE) on the created page if it
* isn't big enough to justify the cost of evicting it. If splits
* continue, it will be merged again until it gets over this limit.
*/
promote = 0;
refcnt = (uint32_t)visit_state.refcnt;
if (refcnt >= WT_MERGE_FULL_PAGE && visit_state.seen_live) {
/*
* In the normal case where there are live children spread
* through the subtree, create two child pages.
*
* Handle the case where the only live child is first / last
* specially: put the live child into the top-level page.
*
* Set SPLIT_MERGE on the internal pages if there are any live
* children: they can't be evicted, so there is no point
* permanently deepening the tree.
*/
if (visit_state.first_live == visit_state.last_live &&
(visit_state.first_live == 0 ||
visit_state.first_live == refcnt - 1))
split = (visit_state.first_live == 0) ? 1 : refcnt - 1;
else
split = (refcnt + 1) / 2;
/* Only promote if we can create a real page. */
if (split == 1 || split == refcnt - 1)
promote = 1;
else if (split >= WT_MERGE_FULL_PAGE &&
visit_state.first_live >= split)
promote = 1;
else if (refcnt - split >= WT_MERGE_FULL_PAGE &&
visit_state.last_live < split)
promote = 1;
}
if (promote) {
/* Create a new top-level split-merge page with two entries. */
WT_ERR(__merge_new_page(session, page_type, 2, 1, &newtop));
visit_state.split = split;
/* Left split. */
if (split == 1)
visit_state.first = newtop;
else {
WT_ERR(__merge_new_page(session, page_type, split,
visit_state.first_live < split, &lchild));
visit_state.first = lchild;
}
/* Right split. */
if (split == refcnt - 1) {
visit_state.second = newtop;
visit_state.second_ref = &newtop->u.intl.t[1];
} else {
WT_ERR(__merge_new_page(session, page_type,
refcnt - split, visit_state.last_live >= split,
&rchild));
visit_state.second = rchild;
visit_state.second_ref =
&visit_state.second->u.intl.t[0];
}
} else {
/*
* Create a new split-merge page for small merges, or if the
* page above is a split merge page. When we do a big enough
* merge, we create a real page at the top and don't consider
* it as a merge candidate again. Over time with an insert
* workload the tree will grow deeper, but that's inevitable,
* and this keeps individual merges small.
*/
WT_ERR(__merge_new_page(session, page_type, refcnt,
refcnt < WT_MERGE_FULL_PAGE ||
__wt_btree_mergeable(top->parent),
&newtop));
visit_state.first = newtop;
}
/*
* Copy the references into the new tree, but don't update anything in
* the locked tree in case there is an error and we need to back out.
* We do this in a separate pass so that we can figure out the key for
* the split point: that allocates memory and so it could still fail.
*/
visit_state.page = visit_state.first;
visit_state.ref = visit_state.page->u.intl.t;
visit_state.refcnt = 0;
WT_ERR(__merge_walk(session, top, 0, __merge_copy_ref, &visit_state));
if (promote) {
/* Promote keys into the top-level page. */
if (lchild != NULL) {
newref = &newtop->u.intl.t[0];
WT_LINK_PAGE(newtop, newref, lchild);
newref->state = WT_REF_MEM;
WT_ERR(__merge_promote_key(session, newref));
}
if (rchild != NULL) {
newref = &newtop->u.intl.t[1];
WT_LINK_PAGE(newtop, newref, rchild);
newref->state = WT_REF_MEM;
WT_ERR(__merge_promote_key(session, newref));
}
}
/*
* We have copied everything into place and allocated all of the memory
* we need. Now link all pages into the new tree and unlock them.
*
* The only way this could fail is if a reference state has been
* changed by another thread since they were locked. Panic in that
* case: that should never happen.
*/
visit_state.page = visit_state.first;
visit_state.ref = visit_state.page->u.intl.t;
visit_state.refcnt = 0;
ret = __merge_walk(session, top, 0, __merge_switch_page, &visit_state);
if (ret != 0)
WT_ERR(__wt_illegal_value(session, "__wt_merge_tree"));
newtop->u.intl.recno = top->u.intl.recno;
newtop->parent = top->parent;
newtop->ref = top->ref;
#ifdef HAVE_DIAGNOSTIC
/*
* Before swapping in the new tree, walk the pages we are discarding,
* check that everything looks right.
*/
__merge_check_discard(session, top);
#endif
/*
* Set up the new top-level page as a split so that it will be swapped
* into place by our caller.
*/
top->modify->flags = WT_PM_REC_SPLIT;
top->modify->u.split = newtop;
WT_VERBOSE_ERR(session, evict,
"Successfully %s %" PRIu32
" split-merge pages containing %" PRIu32 " keys\n",
promote ? "promoted" : "merged", visit_state.maxdepth, refcnt);
/* Evict new child pages as soon as possible. */
if (lchild != NULL && !F_ISSET(lchild->modify, WT_PM_REC_SPLIT_MERGE))
lchild->read_gen = WT_READ_GEN_OLDEST;
if (rchild != NULL && !F_ISSET(rchild->modify, WT_PM_REC_SPLIT_MERGE))
rchild->read_gen = WT_READ_GEN_OLDEST;
/* Update statistics. */
WT_CSTAT_INCR(session, cache_eviction_merge);
WT_DSTAT_INCR(session, cache_eviction_merge);
/* How many levels did we remove? */
levels = visit_state.maxdepth - (promote ? 2 : 1);
WT_CSTAT_INCRV(session, cache_eviction_merge_levels, levels);
WT_DSTAT_INCRV(session, cache_eviction_merge_levels, levels);
return (0);
err: WT_VERBOSE_TRET(session, evict,
"Failed to merge %" PRIu32
" split-merge pages containing %" PRIu32 " keys\n",
visit_state.maxdepth, refcnt);
WT_CSTAT_INCR(session, cache_eviction_merge_fail);
WT_DSTAT_INCR(session, cache_eviction_merge_fail);
if (newtop != NULL)
__wt_page_out(session, &newtop);
if (lchild != NULL)
__wt_page_out(session, &lchild);
if (rchild != NULL)
__wt_page_out(session, &rchild);
return (ret);
}
/*
* __wt_btcur_prev --
* Move to the previous record in the tree.
*/
int
__wt_btcur_prev(WT_CURSOR_BTREE *cbt, int discard)
{
WT_DECL_RET;
WT_PAGE *page;
WT_SESSION_IMPL *session;
uint32_t flags;
int newpage;
session = (WT_SESSION_IMPL *)cbt->iface.session;
WT_DSTAT_INCR(session, cursor_prev);
flags = WT_TREE_SKIP_INTL | WT_TREE_PREV; /* Tree walk flags. */
if (discard)
LF_SET(WT_TREE_DISCARD);
retry: WT_RET(__cursor_func_init(cbt, 0));
__cursor_position_clear(cbt);
/*
* If we aren't already iterating in the right direction, there's
* some setup to do.
*/
if (!F_ISSET(cbt, WT_CBT_ITERATE_PREV))
__wt_btcur_iterate_setup(cbt, 0);
/*
* If this is a modification, we're about to read information from the
* page, save the write generation.
*/
page = cbt->page;
if (discard && page != NULL) {
WT_ERR(__wt_page_modify_init(session, page));
WT_ORDERED_READ(cbt->write_gen, page->modify->write_gen);
}
/*
* Walk any page we're holding until the underlying call returns not-
* found. Then, move to the previous page, until we reach the start
* of the file.
*/
for (newpage = 0;; newpage = 1) {
if (F_ISSET(cbt, WT_CBT_ITERATE_APPEND)) {
switch (page->type) {
case WT_PAGE_COL_FIX:
ret = __cursor_fix_append_prev(cbt, newpage);
break;
case WT_PAGE_COL_VAR:
ret = __cursor_var_append_prev(cbt, newpage);
break;
WT_ILLEGAL_VALUE_ERR(session);
}
if (ret == 0)
break;
F_CLR(cbt, WT_CBT_ITERATE_APPEND);
if (ret != WT_NOTFOUND)
break;
newpage = 1;
}
if (page != NULL) {
switch (page->type) {
case WT_PAGE_COL_FIX:
ret = __cursor_fix_prev(cbt, newpage);
break;
case WT_PAGE_COL_VAR:
ret = __cursor_var_prev(cbt, newpage);
break;
case WT_PAGE_ROW_LEAF:
ret = __cursor_row_prev(cbt, newpage);
break;
WT_ILLEGAL_VALUE_ERR(session);
}
if (ret != WT_NOTFOUND)
break;
}
cbt->page = NULL;
WT_ERR(__wt_tree_walk(session, &page, flags));
WT_ERR_TEST(page == NULL, WT_NOTFOUND);
WT_ASSERT(session,
page->type != WT_PAGE_COL_INT &&
page->type != WT_PAGE_ROW_INT);
cbt->page = page;
/* Initialize the page's modification information */
if (discard) {
WT_ERR(__wt_page_modify_init(session, page));
WT_ORDERED_READ(
cbt->write_gen, page->modify->write_gen);
}
/*
* The last page in a column-store has appended entries.
* We handle it separately from the usual cursor code:
* it's only that one page and it's in a simple format.
*/
if (page->type != WT_PAGE_ROW_LEAF &&
(cbt->ins_head = WT_COL_APPEND(page)) != NULL)
F_SET(cbt, WT_CBT_ITERATE_APPEND);
}
err: if (ret == WT_RESTART)
goto retry;
WT_TRET(__cursor_func_resolve(cbt, ret));
return (ret);
}
/*
* __rec_review --
* Get exclusive access to the page and review the page and its subtree
* for conditions that would block its eviction.
*
* The ref and page arguments may appear to be redundant, because usually
* ref->page == page and page->ref == ref. However, we need both because
* (a) there are cases where ref == NULL (e.g., for root page or during
* salvage), and (b) we can't safely look at page->ref until we have a
* hazard pointer.
*/
static int
__rec_review(WT_SESSION_IMPL *session,
WT_REF *ref, WT_PAGE *page, int exclusive, int merge, int top)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_PAGE_MODIFY *mod;
WT_PAGE *t;
uint32_t i;
btree = session->btree;
/*
* Get exclusive access to the page if our caller doesn't have the tree
* locked down.
*/
if (!exclusive)
WT_RET(__hazard_exclusive(session, ref, top));
/*
* Recurse through the page's subtree: this happens first because we
* have to write pages in depth-first order, otherwise we'll dirty
* pages after we've written them.
*/
if (page->type == WT_PAGE_COL_INT || page->type == WT_PAGE_ROW_INT)
WT_REF_FOREACH(page, ref, i)
switch (ref->state) {
case WT_REF_DISK: /* On-disk */
case WT_REF_DELETED: /* On-disk, deleted */
break;
case WT_REF_MEM: /* In-memory */
WT_RET(__rec_review(session,
ref, ref->page, exclusive, merge, 0));
break;
case WT_REF_EVICT_WALK: /* Walk point */
case WT_REF_EVICT_FORCE: /* Forced evict */
case WT_REF_LOCKED: /* Being evicted */
case WT_REF_READING: /* Being read */
return (EBUSY);
}
/*
* If the file is being checkpointed, we cannot evict dirty pages,
* because that may free a page that appears on an internal page in the
* checkpoint. Don't rely on new updates being skipped by the
* transaction used for transaction reads: (1) there are paths that
* dirty pages for artificial reasons; (2) internal pages aren't
* transactional; and (3) if an update was skipped during the
* checkpoint (leaving the page dirty), then rolled back, we could
* still successfully overwrite a page and corrupt the checkpoint.
*
* Further, even for clean pages, the checkpoint's reconciliation of an
* internal page might race with us as we evict a child in the page's
* subtree.
*
* One half of that test is in the reconciliation code: the checkpoint
* thread waits for eviction-locked pages to settle before determining
* their status. The other half of the test is here: after acquiring
* the exclusive eviction lock on a page, confirm no page in the page's
* stack of pages from the root is being reconciled in a checkpoint.
* This ensures we either see the checkpoint-walk state here, or the
* reconciliation of the internal page sees our exclusive lock on the
* child page and waits until we're finished evicting the child page
* (or give up if eviction isn't possible).
*
* We must check the full stack (we might be attempting to evict a leaf
* page multiple levels beneath the internal page being reconciled as
* part of the checkpoint, and all of the intermediate nodes are being
* merged into the internal page).
*
* There's no simple test for knowing if a page in our page stack is
* involved in a checkpoint. The internal page's checkpoint-walk flag
* is the best test, but it's not set anywhere for the root page, it's
* not a complete test.
*
* Quit for any page that's not a simple, in-memory page. (Almost the
* same as checking for the checkpoint-walk flag. I don't think there
* are code paths that change the page's status from checkpoint-walk,
* but these races are hard enough I'm not going to proceed if there's
* anything other than a vanilla, in-memory tree stack.) Climb until
* we find a page which can't be merged into its parent, and failing if
* we never find such a page.
*/
if (btree->checkpointing && !merge && __wt_page_is_modified(page)) {
ckpt: WT_CSTAT_INCR(session, cache_eviction_checkpoint);
WT_DSTAT_INCR(session, cache_eviction_checkpoint);
return (EBUSY);
}
if (btree->checkpointing && top)
for (t = page->parent;; t = t->parent) {
if (t == NULL || t->ref == NULL) /* root */
goto ckpt;
if (t->ref->state != WT_REF_MEM) /* scary */
goto ckpt;
if (t->modify == NULL || /* not merged */
!F_ISSET(t->modify, WT_PM_REC_EMPTY |
WT_PM_REC_SPLIT | WT_PM_REC_SPLIT_MERGE))
break;
}
/*
* If we are merging internal pages, we just need exclusive access, we
* don't need to write everything.
*/
if (merge)
return (0);
/*
* Fail if any page in the top-level page's subtree won't be merged into
* its parent, the page that cannot be merged must be evicted first.
* The test is necessary but should not fire much: the eviction code is
* biased for leaf pages, an internal page shouldn't be selected for
* eviction until its children have been evicted.
*
* We have to write dirty pages to know their final state, a page marked
* empty may have had records added since reconciliation, a page marked
* split may have had records deleted and no longer need to split.
* Split-merge pages are the exception: they can never be change into
* anything other than a split-merge page and are merged regardless of
* being clean or dirty.
*
* Writing the page is expensive, do a cheap test first: if it doesn't
* appear a subtree page can be merged, quit. It's possible the page
* has been emptied since it was last reconciled, and writing it before
* testing might be worthwhile, but it's more probable we're attempting
* to evict an internal page with live children, and that's a waste of
* time.
*/
mod = page->modify;
if (!top && (mod == NULL || !F_ISSET(mod,
WT_PM_REC_EMPTY | WT_PM_REC_SPLIT | WT_PM_REC_SPLIT_MERGE)))
return (EBUSY);
/*
* If the page is dirty and can possibly change state, write it so we
* know the final state.
*/
if (__wt_page_is_modified(page) &&
!F_ISSET(mod, WT_PM_REC_SPLIT_MERGE)) {
ret = __wt_rec_write(session, page,
NULL, WT_EVICTION_SERVER_LOCKED | WT_SKIP_UPDATE_QUIT);
/*
* Update the page's modification reference, reconciliation
* might have changed it.
*/
mod = page->modify;
/* If there are unwritten changes on the page, give up. */
if (ret == EBUSY) {
WT_VERBOSE_RET(session, evict,
"eviction failed, reconciled page not clean");
/*
* We may be able to discard any "update" memory the
* page no longer needs.
*/
switch (page->type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
__wt_col_leaf_obsolete(session, page);
break;
case WT_PAGE_ROW_LEAF:
__wt_row_leaf_obsolete(session, page);
break;
}
}
WT_RET(ret);
WT_ASSERT(session, __wt_page_is_modified(page) == 0);
}
/*
* Repeat the test: fail if any page in the top-level page's subtree
* won't be merged into its parent.
*/
if (!top && (mod == NULL || !F_ISSET(mod,
WT_PM_REC_EMPTY | WT_PM_REC_SPLIT | WT_PM_REC_SPLIT_MERGE)))
return (EBUSY);
return (0);
}
/*
* __wt_rec_evict --
* Reconciliation plus eviction.
*/
int
__wt_rec_evict(WT_SESSION_IMPL *session, WT_PAGE *page, int exclusive)
{
WT_DECL_RET;
WT_PAGE_MODIFY *mod;
int merge;
WT_VERBOSE_RET(session, evict,
"page %p (%s)", page, __wt_page_type_string(page->type));
WT_ASSERT(session, session->excl_next == 0);
/*
* If we get a split-merge page during normal eviction, try to collapse
* it. During close, it will be merged into its parent.
*/
mod = page->modify;
merge = __wt_btree_mergeable(page);
if (merge && exclusive)
return (EBUSY);
WT_ASSERT(session, merge || mod == NULL ||
!F_ISSET(mod, WT_PM_REC_SPLIT_MERGE));
/*
* Get exclusive access to the page and review the page and its subtree
* for conditions that would block our eviction of the page. If the
* check fails (for example, we find a child page that can't be merged),
* we're done. We have to make this check for clean pages, too: while
* unlikely eviction would choose an internal page with children, it's
* not disallowed anywhere.
*
* Note that page->ref may be NULL in some cases (e.g., for root pages
* or during salvage). That's OK if exclusive is set: we won't check
* hazard pointers in that case.
*/
WT_ERR(__rec_review(session, page->ref, page, exclusive, merge, 1));
/* Try to merge internal pages. */
if (merge)
WT_ERR(__wt_merge_tree(session, page));
/*
* Update the page's modification reference, reconciliation might have
* changed it.
*/
mod = page->modify;
/* Count evictions of internal pages during normal operation. */
if (!exclusive && !merge &&
(page->type == WT_PAGE_COL_INT || page->type == WT_PAGE_ROW_INT)) {
WT_CSTAT_INCR(session, cache_eviction_internal);
WT_DSTAT_INCR(session, cache_eviction_internal);
}
/*
* Update the parent and discard the page.
*/
if (mod == NULL || !F_ISSET(mod, WT_PM_REC_MASK)) {
WT_ASSERT(session,
exclusive || page->ref->state == WT_REF_LOCKED);
if (WT_PAGE_IS_ROOT(page))
__rec_root_update(session);
else
__rec_page_clean_update(session, page);
/* Discard the page. */
__rec_discard_page(session, page, exclusive);
WT_CSTAT_INCR(session, cache_eviction_clean);
WT_DSTAT_INCR(session, cache_eviction_clean);
} else {
if (WT_PAGE_IS_ROOT(page))
__rec_root_update(session);
else
WT_ERR(__rec_page_dirty_update(session, page));
/* Discard the tree rooted in this page. */
__rec_discard_tree(session, page, exclusive);
WT_CSTAT_INCR(session, cache_eviction_dirty);
WT_DSTAT_INCR(session, cache_eviction_dirty);
}
if (0) {
err: /*
* If unable to evict this page, release exclusive reference(s)
* we've acquired.
*/
__rec_excl_clear(session);
WT_CSTAT_INCR(session, cache_eviction_fail);
WT_DSTAT_INCR(session, cache_eviction_fail);
}
session->excl_next = 0;
return (ret);
}
/*
* __wt_bt_read --
* Read a cookie referenced block into a buffer.
*/
int
__wt_bt_read(WT_SESSION_IMPL *session,
WT_ITEM *buf, const uint8_t *addr, uint32_t addr_size)
{
WT_BM *bm;
WT_BTREE *btree;
WT_DECL_ITEM(tmp);
WT_DECL_RET;
WT_PAGE_HEADER *dsk;
size_t result_len;
btree = session->btree;
bm = btree->bm;
/*
* If anticipating a compressed block, read into a scratch buffer and
* decompress into the caller's buffer. Else, read directly into the
* caller's buffer.
*/
if (btree->compressor == NULL) {
WT_RET(bm->read(bm, session, buf, addr, addr_size));
dsk = buf->mem;
} else {
WT_RET(__wt_scr_alloc(session, 0, &tmp));
WT_ERR(bm->read(bm, session, tmp, addr, addr_size));
dsk = tmp->mem;
}
/*
* If the block is compressed, copy the skipped bytes of the original
* image into place, then decompress.
*/
if (F_ISSET(dsk, WT_PAGE_COMPRESSED)) {
if (btree->compressor == NULL ||
btree->compressor->decompress == NULL)
WT_ERR_MSG(session, WT_ERROR,
"read compressed block where no compression engine "
"configured");
/*
* We're allocating the exact number of bytes we're expecting
* from decompression.
*/
WT_ERR(__wt_buf_init(session, buf, dsk->mem_size));
buf->size = dsk->mem_size;
/*
* Note the source length is NOT the number of compressed bytes,
* it's the length of the block we just read (minus the skipped
* bytes). We don't store the number of compressed bytes: some
* compression engines need that length stored externally, they
* don't have markers in the stream to signal the end of the
* compressed bytes. Those engines must store the compressed
* byte length somehow, see the snappy compression extension for
* an example.
*/
memcpy(buf->mem, tmp->mem, WT_BLOCK_COMPRESS_SKIP);
WT_ERR(btree->compressor->decompress(
btree->compressor, &session->iface,
(uint8_t *)tmp->mem + WT_BLOCK_COMPRESS_SKIP,
tmp->size - WT_BLOCK_COMPRESS_SKIP,
(uint8_t *)buf->mem + WT_BLOCK_COMPRESS_SKIP,
dsk->mem_size - WT_BLOCK_COMPRESS_SKIP,
&result_len));
/*
* If checksums were turned off because we're depending on the
* decompression to fail on any corrupted data, we'll end up
* here after corruption happens. If we're salvaging the file,
* it's OK, otherwise it's really, really bad.
*/
if (result_len != dsk->mem_size - WT_BLOCK_COMPRESS_SKIP)
WT_ERR(
F_ISSET(session, WT_SESSION_SALVAGE_QUIET_ERR) ?
WT_ERROR :
__wt_illegal_value(session, btree->name));
} else
if (btree->compressor == NULL)
buf->size = dsk->mem_size;
else
/*
* We guessed wrong: there was a compressor, but this
* block was not compressed, and now the page is in the
* wrong buffer and the buffer may be of the wrong size.
* This should be rare, but happens with small blocks
* that aren't worth compressing.
*/
WT_ERR(__wt_buf_set(
session, buf, tmp->data, dsk->mem_size));
/* If the handle is a verify handle, verify the physical page. */
if (F_ISSET(btree, WT_BTREE_VERIFY)) {
if (tmp == NULL)
WT_ERR(__wt_scr_alloc(session, 0, &tmp));
WT_ERR(bm->addr_string(bm, session, tmp, addr, addr_size));
WT_ERR(__wt_verify_dsk(session, (const char *)tmp->data, buf));
}
WT_CSTAT_INCR(session, cache_read);
WT_DSTAT_INCR(session, cache_read);
if (F_ISSET(dsk, WT_PAGE_COMPRESSED))
WT_DSTAT_INCR(session, compress_read);
WT_CSTAT_INCRV(session, cache_bytes_read, addr_size);
WT_DSTAT_INCRV(session, cache_bytes_read, addr_size);
err: __wt_scr_free(&tmp);
return (ret);
}
/*
* __wt_bt_write --
* Write a buffer into a block, returning the block's addr/size and
* checksum.
*/
int
__wt_bt_write(WT_SESSION_IMPL *session, WT_ITEM *buf,
uint8_t *addr, uint32_t *addr_size, int checkpoint, int compressed)
{
WT_BM *bm;
WT_BTREE *btree;
WT_ITEM *ip;
WT_DECL_ITEM(tmp);
WT_DECL_RET;
WT_PAGE_HEADER *dsk;
size_t len, src_len, dst_len, result_len, size;
int data_cksum, compression_failed;
uint8_t *src, *dst;
btree = session->btree;
bm = btree->bm;
/* Checkpoint calls are different than standard calls. */
WT_ASSERT(session,
(checkpoint == 0 && addr != NULL && addr_size != NULL) ||
(checkpoint == 1 && addr == NULL && addr_size == NULL));
#ifdef HAVE_DIAGNOSTIC
/*
* We're passed a table's disk image. Decompress if necessary and
* verify the image. Always check the in-memory length for accuracy.
*/
dsk = buf->mem;
if (compressed) {
WT_ERR(__wt_scr_alloc(session, dsk->mem_size, &tmp));
memcpy(tmp->mem, buf->data, WT_BLOCK_COMPRESS_SKIP);
WT_ERR(btree->compressor->decompress(
btree->compressor, &session->iface,
(uint8_t *)buf->data + WT_BLOCK_COMPRESS_SKIP,
buf->size - WT_BLOCK_COMPRESS_SKIP,
(uint8_t *)tmp->data + WT_BLOCK_COMPRESS_SKIP,
tmp->memsize - WT_BLOCK_COMPRESS_SKIP,
&result_len));
WT_ASSERT(session,
dsk->mem_size == result_len + WT_BLOCK_COMPRESS_SKIP);
tmp->size = (uint32_t)result_len + WT_BLOCK_COMPRESS_SKIP;
ip = tmp;
} else {
WT_ASSERT(session, dsk->mem_size == buf->size);
ip = buf;
}
WT_ERR(__wt_verify_dsk(session, "[write-check]", ip));
__wt_scr_free(&tmp);
#endif
/*
* Optionally stream-compress the data, but don't compress blocks that
* are already as small as they're going to get.
*/
if (buf->size <= btree->allocsize ||
btree->compressor == NULL ||
btree->compressor->compress == NULL || compressed) {
ip = buf;
WT_DSTAT_INCR(session, compress_write_too_small);
} else {
/* Skip the header bytes of the source data. */
src = (uint8_t *)buf->mem + WT_BLOCK_COMPRESS_SKIP;
src_len = buf->size - WT_BLOCK_COMPRESS_SKIP;
/*
* Compute the size needed for the destination buffer. We only
* allocate enough memory for a copy of the original by default,
* if any compressed version is bigger than the original, we
* won't use it. However, some compression engines (snappy is
* one example), may need more memory because they don't stop
* just because there's no more memory into which to compress.
*/
if (btree->compressor->pre_size == NULL)
len = src_len;
else
WT_ERR(btree->compressor->pre_size(btree->compressor,
&session->iface, src, src_len, &len));
size = len + WT_BLOCK_COMPRESS_SKIP;
WT_ERR(bm->write_size(bm, session, &size));
WT_ERR(__wt_scr_alloc(session, size, &tmp));
/* Skip the header bytes of the destination data. */
dst = (uint8_t *)tmp->mem + WT_BLOCK_COMPRESS_SKIP;
dst_len = len;
/*
* If compression fails, fallback to the original version. This
* isn't unexpected: if compression doesn't work for some chunk
* of bytes for some reason (noting there's likely additional
* format/header information which compressed output requires),
* it just means the uncompressed version is as good as it gets,
* and that's what we use.
*/
compression_failed = 0;
WT_ERR(btree->compressor->compress(btree->compressor,
&session->iface,
src, src_len,
dst, dst_len,
&result_len, &compression_failed));
if (compression_failed) {
ip = buf;
WT_DSTAT_INCR(session, compress_write_fail);
} else {
compressed = 1;
WT_DSTAT_INCR(session, compress_write);
/*
* Copy in the skipped header bytes, set the final data
* size.
*/
memcpy(tmp->mem, buf->mem, WT_BLOCK_COMPRESS_SKIP);
tmp->size =
(uint32_t)result_len + WT_BLOCK_COMPRESS_SKIP;
ip = tmp;
}
}
dsk = ip->mem;
/* If the buffer is compressed, set the flag. */
if (compressed)
F_SET(dsk, WT_PAGE_COMPRESSED);
/*
* We increment the block's write generation so it's easy to identify
* newer versions of blocks during salvage. (It's common in WiredTiger,
* at least for the default block manager, for multiple blocks to be
* internally consistent with identical first and last keys, so we need
* a way to know the most recent state of the block. We could check
* which leaf is referenced by a valid internal page, but that implies
* salvaging internal pages, which I don't want to do, and it's not
* as good anyway, because the internal page may not have been written
* after the leaf page was updated. So, write generations it is.
*
* Nothing is locked at this point but two versions of a page with the
* same generation is pretty unlikely, and if we did, they're going to
* be roughly identical for the purposes of salvage, anyway.
*/
dsk->write_gen = ++btree->write_gen;
/*
* Checksum the data if the buffer isn't compressed or checksums are
* configured.
*/
switch (btree->checksum) {
case CKSUM_ON:
data_cksum = 1;
break;
case CKSUM_OFF:
data_cksum = 0;
break;
case CKSUM_UNCOMPRESSED:
default:
data_cksum = !compressed;
break;
}
/* Call the block manager to write the block. */
WT_ERR(checkpoint ?
bm->checkpoint(bm, session, ip, btree->ckpt, data_cksum) :
bm->write(bm, session, ip, addr, addr_size, data_cksum));
WT_CSTAT_INCR(session, cache_write);
WT_DSTAT_INCR(session, cache_write);
WT_CSTAT_INCRV(session, cache_bytes_write, ip->size);
WT_DSTAT_INCRV(session, cache_bytes_write, ip->size);
err: __wt_scr_free(&tmp);
return (ret);
}
/*
* __wt_compact_evict --
* Helper routine to decide if a file's size would benefit from re-writing
* this page.
*/
int
__wt_compact_evict(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_BM *bm;
WT_PAGE_MODIFY *mod;
int skip;
uint32_t addr_size;
const uint8_t *addr;
bm = S2BT(session)->bm;
mod = page->modify;
/*
* We have to review page reconciliation information as an in-memory
* page's original disk addresses might have been fine for compaction
* but its replacement addresses might be a problem. To review page
* reconciliation information, we have to lock out both eviction and
* checkpoints, as those are the other two operations that can write
* a page.
*
* Ignore the root: it may not have a replacement address, and besides,
* if anything else gets written, so will it.
*/
if (WT_PAGE_IS_ROOT(page))
return (0);
/*
* If the page is already dirty, skip some work, it will be written in
* any case.
*/
if (__wt_page_is_modified(page))
return (0);
/*
* If the page is clean, test the original addresses.
* If the page is a 1-to-1 replacement, test the replacement addresses.
* If the page is a split, ignore it, it will be merged into the parent.
*/
if (mod == NULL)
goto disk;
switch (F_ISSET(mod, WT_PM_REC_MASK)) {
case 0:
disk: __wt_get_addr(page->parent, page->ref, &addr, &addr_size);
if (addr == NULL)
return (0);
WT_RET(
bm->compact_page_skip(bm, session, addr, addr_size, &skip));
if (skip)
return (0);
break;
case WT_PM_REC_EMPTY:
return (0);
case WT_PM_REC_REPLACE:
WT_RET(bm->compact_page_skip(bm,
session, mod->u.replace.addr, mod->u.replace.size, &skip));
if (skip)
return (0);
break;
case WT_PM_REC_SPLIT:
case WT_PM_REC_SPLIT_MERGE:
return (0);
}
/* Mark the page and tree dirty, we want to write this page. */
WT_RET(__wt_page_modify_init(session, page));
__wt_page_and_tree_modify_set(session, page);
WT_DSTAT_INCR(session, btree_compact_rewrite);
return (0);
}
