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journal: optimize bisection logic a bit by caching the last position

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This way we can do a quick restart limiting a bit how wildly we need to
jump around during the bisection process.
This commit is contained in:
Lennart Poettering 2013-11-26 20:37:53 +01:00
parent bf807d4dbf
commit f268980d2c
Notes: Zbigniew Jędrzejewski-Szmek 2013-12-03 18:52:22 -05:00 
Backport: performance
1 changed files with 98 additions and 34 deletions
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132
src/journal/journal-file.c
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@ -1366,6 +1366,7 @@ typedef struct ChainCacheItem {
uint64_t array; /* the cached array */
uint64_t begin; /* the first item in the cached array */
uint64_t total; /* the total number of items in all arrays before this one in the chain */
uint64_t last_index; /* the last index we looked at, to optimize locality when bisecting */
} ChainCacheItem;
static void chain_cache_put(
@ -1374,7 +1375,8 @@ static void chain_cache_put(
uint64_t first,
uint64_t array,
uint64_t begin,
uint64_t total) {
uint64_t total,
uint64_t last_index) {
if (!ci) {
/* If the chain item to cache for this chain is the
@ -1402,12 +1404,14 @@ static void chain_cache_put(
ci->array = array;
ci->begin = begin;
ci->total = total;
ci->last_index = last_index;
}
static int generic_array_get(JournalFile *f,
uint64_t first,
uint64_t i,
Object **ret, uint64_t *offset) {
static int generic_array_get(
JournalFile *f,
uint64_t first,
uint64_t i,
Object **ret, uint64_t *offset) {
Object *o;
uint64_t p = 0, a, t = 0;
@ -1448,7 +1452,7 @@ static int generic_array_get(JournalFile *f,
found:
/* Let's cache this item for the next invocation */
chain_cache_put(f->chain_cache, ci, first, a, o->entry_array.items[0], t);
chain_cache_put(f->chain_cache, ci, first, a, o->entry_array.items[0], t, i);
r = journal_file_move_to_object(f, OBJECT_ENTRY, p, &o);
if (r < 0)
@ -1463,11 +1467,12 @@ found:
return 1;
}
static int generic_array_get_plus_one(JournalFile *f,
uint64_t extra,
uint64_t first,
uint64_t i,
Object **ret, uint64_t *offset) {
static int generic_array_get_plus_one(
JournalFile *f,
uint64_t extra,
uint64_t first,
uint64_t i,
Object **ret, uint64_t *offset) {
Object *o;
@ -1498,17 +1503,18 @@ enum {
TEST_RIGHT
};
static int generic_array_bisect(JournalFile *f,
uint64_t first,
uint64_t n,
uint64_t needle,
int (*test_object)(JournalFile *f, uint64_t p, uint64_t needle),
direction_t direction,
Object **ret,
uint64_t *offset,
uint64_t *idx) {
static int generic_array_bisect(
JournalFile *f,
uint64_t first,
uint64_t n,
uint64_t needle,
int (*test_object)(JournalFile *f, uint64_t p, uint64_t needle),
direction_t direction,
Object **ret,
uint64_t *offset,
uint64_t *idx) {
uint64_t a, p, t = 0, i = 0, last_p = 0;
uint64_t a, p, t = 0, i = 0, last_p = 0, last_index = (uint64_t) -1;
bool subtract_one = false;
Object *o, *array = NULL;
int r;
@ -1533,7 +1539,7 @@ static int generic_array_bisect(JournalFile *f,
return r;
if (r == TEST_LEFT) {
/* OK, what we are looking for is right of th
/* OK, what we are looking for is right of the
* begin of this EntryArray, so let's jump
* straight to previously cached array in the
* chain */
@ -1541,6 +1547,7 @@ static int generic_array_bisect(JournalFile *f,
a = ci->array;
n -= ci->total;
t = ci->total;
last_index = ci->last_index;
}
}
@ -1571,6 +1578,60 @@ static int generic_array_bisect(JournalFile *f,
if (r == TEST_RIGHT) {
left = 0;
right -= 1;
if (last_index != (uint64_t) -1) {
assert(last_index <= right);
/* If we cached the last index we
* looked at, let's try to not to jump
* too wildly around and see if we can
* limit the range to look at early to
* the immediate neighbors of the last
* index we looked at. */
if (last_index > 0) {
uint64_t x = last_index - 1;
p = le64toh(array->entry_array.items[x]);
if (p <= 0)
return -EBADMSG;
r = test_object(f, p, needle);
if (r < 0)
return r;
if (r == TEST_FOUND)
r = direction == DIRECTION_DOWN ? TEST_RIGHT : TEST_LEFT;
if (r == TEST_RIGHT)
right = x;
else
left = x + 1;
}
if (last_index < right) {
uint64_t y = last_index + 1;
p = le64toh(array->entry_array.items[y]);
if (p <= 0)
return -EBADMSG;
r = test_object(f, p, needle);
if (r < 0)
return r;
if (r == TEST_FOUND)
r = direction == DIRECTION_DOWN ? TEST_RIGHT : TEST_LEFT;
if (r == TEST_RIGHT)
right = y;
else
left = y + 1;
}
last_index = (uint64_t) -1;
}
for (;;) {
if (left == right) {
if (direction == DIRECTION_UP)
@ -1581,8 +1642,8 @@ static int generic_array_bisect(JournalFile *f,
}
assert(left < right);
i = (left + right) / 2;
p = le64toh(array->entry_array.items[i]);
if (p <= 0)
return -EBADMSG;
@ -1615,6 +1676,7 @@ static int generic_array_bisect(JournalFile *f,
n -= k;
t += k;
last_index = (uint64_t) -1;
a = le64toh(array->entry_array.next_entry_array_offset);
}
@ -1625,7 +1687,7 @@ found:
return 0;
/* Let's cache this item for the next invocation */
chain_cache_put(f->chain_cache, ci, first, a, array->entry_array.items[0], t);
chain_cache_put(f->chain_cache, ci, first, a, array->entry_array.items[0], t, i + (subtract_one ? -1 : 0));
if (subtract_one && i == 0)
p = last_p;
@ -1650,16 +1712,18 @@ found:
return 1;
}
static int generic_array_bisect_plus_one(JournalFile *f,
uint64_t extra,
uint64_t first,
uint64_t n,
uint64_t needle,
int (*test_object)(JournalFile *f, uint64_t p, uint64_t needle),
direction_t direction,
Object **ret,
uint64_t *offset,
uint64_t *idx) {
static int generic_array_bisect_plus_one(
JournalFile *f,
uint64_t extra,
uint64_t first,
uint64_t n,
uint64_t needle,
int (*test_object)(JournalFile *f, uint64_t p, uint64_t needle),
direction_t direction,
Object **ret,
uint64_t *offset,
uint64_t *idx) {
int r;
bool step_back = false;