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Merge pull request #2260 from wiredtiger/reverse-splits

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SERVER-21027 Reverse split if there are many deleted pages
This commit is contained in:
Alex Gorrod
2015-10-29 12:06:03 +11:00
parent ed9c0d6fc8 b564700ba2
commit 35d46c3a0e
10 changed files with 108 additions and 29 deletions
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1
dist/flags.py vendored
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@@ -36,6 +36,7 @@ flags = {
'page_read' : [
'READ_CACHE',
'READ_COMPACT',
'READ_NO_EMPTY',
'READ_NO_EVICT',
'READ_NO_GEN',
'READ_NO_WAIT',

10
src/btree/bt_delete.c
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@@ -214,10 +214,11 @@ __wt_delete_page_rollback(WT_SESSION_IMPL *session, WT_REF *ref)
/*
* __wt_delete_page_skip --
* If iterating a cursor, skip deleted pages that are visible to us.
* If iterating a cursor, skip deleted pages that are either visible to
* us or globally visible.
*/
bool
__wt_delete_page_skip(WT_SESSION_IMPL *session, WT_REF *ref)
__wt_delete_page_skip(WT_SESSION_IMPL *session, WT_REF *ref, bool visible_all)
{
bool skip;
@@ -245,8 +246,9 @@ __wt_delete_page_skip(WT_SESSION_IMPL *session, WT_REF *ref)
if (!__wt_atomic_casv32(&ref->state, WT_REF_DELETED, WT_REF_LOCKED))
return (false);
skip = ref->page_del == NULL ||
__wt_txn_visible(session, ref->page_del->txnid);
skip = ref->page_del == NULL || (visible_all ?
__wt_txn_visible_all(session, ref->page_del->txnid) :
__wt_txn_visible(session, ref->page_del->txnid));
WT_PUBLISH(ref->state, WT_REF_DELETED);
return (skip);

6
src/btree/bt_read.c
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@@ -448,8 +448,12 @@ __wt_page_in_func(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t flags
for (oldgen = stalled = false,
force_attempts = 0, sleep_cnt = wait_cnt = 0;;) {
switch (ref->state) {
case WT_REF_DISK:
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);

40
src/btree/bt_split.c
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@@ -1010,11 +1010,12 @@ __split_parent(WT_SESSION_IMPL *session, WT_REF *ref,
* reading thread will restart. Include the ref we are splitting in
* the count to be deleted.
*/
for (i = 0, deleted_entries = 1; i < parent_entries; ++i) {
deleted_entries = ref_new != NULL ? 1 : 0;
for (i = 0; i < parent_entries; ++i) {
next_ref = pindex->index[i];
WT_ASSERT(session, next_ref->state != WT_REF_SPLIT);
if (next_ref->state == WT_REF_DELETED &&
__wt_delete_page_skip(session, next_ref) &&
__wt_delete_page_skip(session, next_ref, true) &&
__wt_atomic_casv32(
&next_ref->state, WT_REF_DELETED, WT_REF_SPLIT))
deleted_entries++;
@@ -1026,6 +1027,18 @@ __split_parent(WT_SESSION_IMPL *session, WT_REF *ref,
*/
result_entries = (parent_entries + new_entries) - deleted_entries;
/*
* If the entire (sub)tree is empty, leave the first ref in place,
* deleted.
*/
if (result_entries == 0) {
next_ref = pindex->index[0];
WT_ASSERT(session, next_ref->state == WT_REF_SPLIT);
next_ref->state = WT_REF_DELETED;
--deleted_entries;
result_entries = 1;
}
/*
* Allocate and initialize a new page index array for the parent, then
* copy references from the original index array, plus references from
@@ -1507,6 +1520,29 @@ __wt_split_insert(WT_SESSION_IMPL *session, WT_REF *ref)
return (ret);
}
/*
* __wt_split_reverse --
* Lock, then reverse split an internal page (remove deleted refs).
*/
int
__wt_split_reverse(WT_SESSION_IMPL *session, WT_REF *ref)
{
WT_DECL_RET;
WT_PAGE *parent;
WT_REF dummy_child;
bool hazard;
WT_CLEAR(dummy_child);
dummy_child.home = dummy_child.page = ref->page;
dummy_child.state = WT_REF_MEM;
WT_RET(__split_parent_lock(session, &dummy_child, &parent, &hazard));
WT_ASSERT(session, parent == ref->page);
ret = __split_parent(session, &dummy_child, NULL, 0, 0, 0);
WT_TRET(__split_parent_unlock(session, parent, hazard));
return (ret);
}
/*
* __wt_split_rewrite --
* Rewrite an in-memory page with a new version.

14
src/btree/bt_walk.c
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@@ -94,6 +94,9 @@ __wt_tree_walk(WT_SESSION_IMPL *session,
*/
WT_ENTER_PAGE_INDEX(session);
/* Walk should never instantiate deleted pages. */
LF_SET(WT_READ_NO_EMPTY);
/*
* !!!
* Fast-truncate currently only works on row-store trees.
@@ -174,9 +177,10 @@ ascend: /*
/*
* If we got all the way through an internal page and
* all of the child pages were deleted, evict it.
* all of the child pages were deleted, mark it for
* eviction.
*/
if (empty_internal) {
if (empty_internal && pindex->entries > 1) {
__wt_page_evict_soon(ref->page);
empty_internal = false;
}
@@ -257,7 +261,7 @@ ascend: /*
* to delete it again.
*/
if (ref->state == WT_REF_DELETED &&
__wt_delete_page_skip(session, ref))
__wt_delete_page_skip(session, ref, false))
break;
/*
* If deleting a range, try to delete the page
@@ -294,7 +298,7 @@ ascend: /*
* Try to skip deleted pages visible to us.
*/
if (ref->state == WT_REF_DELETED &&
__wt_delete_page_skip(session, ref))
__wt_delete_page_skip(session, ref, false))
break;
}
@@ -302,7 +306,7 @@ ascend: /*
/*
* Not-found is an expected return when only walking
* in-cache pages.
* in-cache pages, or if we see a deleted page.
*/
if (ret == WT_NOTFOUND) {
ret = 0;

37
src/evict/evict_page.c
View File

@@ -142,6 +142,28 @@ done: if (((inmem_split && ret == 0) || (forced_eviction && ret == EBUSY)) &&
return (ret);
}
/*
* __evict_reverse_split_check --
* Check if an internal page needs a reverse split.
*/
static int
__evict_reverse_split_check(WT_SESSION_IMPL *session, WT_REF *ref)
{
WT_PAGE *parent;
WT_PAGE_INDEX *pindex;
uint32_t deleted_entries;
if (__wt_ref_is_root(ref))
return (0);
parent = ref->home;
WT_INTL_INDEX_GET(session, parent, pindex);
deleted_entries = __wt_atomic_addv32(&pindex->deleted_entries, 1);
if (deleted_entries > pindex->entries / 10)
WT_RET(__wt_split_reverse(session, parent->pg_intl_parent_ref));
return (0);
}
/*
* __wt_evict_page_clean_update --
@@ -151,6 +173,8 @@ int
__wt_evict_page_clean_update(
WT_SESSION_IMPL *session, WT_REF *ref, bool closing)
{
WT_DECL_RET;
/*
* If doing normal system eviction, but only in the service of reducing
* the number of dirty pages, leave the clean page in cache.
@@ -164,8 +188,13 @@ __wt_evict_page_clean_update(
* page re-instantiated (for example, by searching) and never written.
*/
__wt_ref_out(session, ref);
WT_PUBLISH(ref->state,
ref->addr == NULL ? WT_REF_DELETED : WT_REF_DISK);
if (ref->addr == NULL) {
WT_PUBLISH(ref->state, WT_REF_DELETED);
WT_WITH_PAGE_INDEX(session,
ret = __evict_reverse_split_check(session, ref));
WT_RET_BUSY_OK(ret);
} else
WT_PUBLISH(ref->state, WT_REF_DISK);
return (0);
}
@@ -178,6 +207,7 @@ static int
__evict_page_dirty_update(WT_SESSION_IMPL *session, WT_REF *ref, bool closing)
{
WT_ADDR *addr;
WT_DECL_RET;
WT_PAGE *parent;
WT_PAGE_MODIFY *mod;
@@ -207,6 +237,9 @@ __evict_page_dirty_update(WT_SESSION_IMPL *session, WT_REF *ref, bool closing)
__wt_ref_out(session, ref);
ref->addr = NULL;
WT_PUBLISH(ref->state, WT_REF_DELETED);
WT_WITH_PAGE_INDEX(session,
ret = __evict_reverse_split_check(session, ref));
WT_RET_BUSY_OK(ret);
break;
case WT_PM_REC_MULTIBLOCK: /* Multiple blocks */
/*

1
src/include/btmem.h
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@@ -432,6 +432,7 @@ struct __wt_page {
struct __wt_page_index {
uint32_t entries;
uint32_t deleted_entries;
WT_REF **index;
} * volatile __index; /* Collated children */

10
src/include/btree.i
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@@ -1263,13 +1263,9 @@ __wt_page_swap_func(WT_SESSION_IMPL *session, WT_REF *held,
#endif
);
/* An expected failure: WT_NOTFOUND when doing a cache-only read. */
if (LF_ISSET(WT_READ_CACHE) && ret == WT_NOTFOUND)
return (WT_NOTFOUND);
/* An expected failure: WT_RESTART */
if (ret == WT_RESTART)
return (WT_RESTART);
/* Expected failures: page not found or restart. */
if (ret == WT_NOTFOUND || ret == WT_RESTART)
return (ret);
/* Discard the original held page. */
acquired = ret == 0;

3
src/include/extern.h
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@@ -116,7 +116,7 @@ extern int __wt_debug_tree( WT_SESSION_IMPL *session, WT_BTREE *btree, WT_PAGE *
extern int __wt_debug_page(WT_SESSION_IMPL *session, WT_PAGE *page, const char *ofile);
extern int __wt_delete_page(WT_SESSION_IMPL *session, WT_REF *ref, bool *skipp);
extern void __wt_delete_page_rollback(WT_SESSION_IMPL *session, WT_REF *ref);
extern bool __wt_delete_page_skip(WT_SESSION_IMPL *session, WT_REF *ref);
extern bool __wt_delete_page_skip(WT_SESSION_IMPL *session, WT_REF *ref, bool visible_all);
extern int __wt_delete_page_instantiate(WT_SESSION_IMPL *session, WT_REF *ref);
extern void __wt_ref_out(WT_SESSION_IMPL *session, WT_REF *ref);
extern void __wt_page_out(WT_SESSION_IMPL *session, WT_PAGE **pagep);
@@ -155,6 +155,7 @@ extern void __wt_split_stash_discard(WT_SESSION_IMPL *session);
extern void __wt_split_stash_discard_all( WT_SESSION_IMPL *session_safe, WT_SESSION_IMPL *session);
extern int __wt_multi_to_ref(WT_SESSION_IMPL *session, WT_PAGE *page, WT_MULTI *multi, WT_REF **refp, size_t *incrp);
extern int __wt_split_insert(WT_SESSION_IMPL *session, WT_REF *ref);
extern int __wt_split_reverse(WT_SESSION_IMPL *session, WT_REF *ref);
extern int __wt_split_rewrite(WT_SESSION_IMPL *session, WT_REF *ref);
extern int __wt_split_multi(WT_SESSION_IMPL *session, WT_REF *ref, int closing);
extern int __wt_btree_stat_init(WT_SESSION_IMPL *session, WT_CURSOR_STAT *cst);

15
src/include/flags.h
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@@ -36,13 +36,14 @@
#define WT_LOG_FSYNC 0x00000008
#define WT_READ_CACHE 0x00000001
#define WT_READ_COMPACT 0x00000002
#define WT_READ_NO_EVICT 0x00000004
#define WT_READ_NO_GEN 0x00000008
#define WT_READ_NO_WAIT 0x00000010
#define WT_READ_PREV 0x00000020
#define WT_READ_SKIP_INTL 0x00000040
#define WT_READ_TRUNCATE 0x00000080
#define WT_READ_WONT_NEED 0x00000100
#define WT_READ_NO_EMPTY 0x00000004
#define WT_READ_NO_EVICT 0x00000008
#define WT_READ_NO_GEN 0x00000010
#define WT_READ_NO_WAIT 0x00000020
#define WT_READ_PREV 0x00000040
#define WT_READ_SKIP_INTL 0x00000080
#define WT_READ_TRUNCATE 0x00000100
#define WT_READ_WONT_NEED 0x00000200
#define WT_SESSION_CAN_WAIT 0x00000001
#define WT_SESSION_CLEAR_EVICT_WALK 0x00000002
#define WT_SESSION_INTERNAL 0x00000004