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Added rbyd < 1/4 block_size condition to btree merges

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This just avoids the overhead of estimating our sibling's sizes, which
we don't really want to do every compact.
This commit is contained in:
Christopher Haster
2023-08-20 01:18:05 -05:00
parent bacd09a673
commit 105a0a12ce
1 changed files with 72 additions and 67 deletions
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lfs.c
+72 -67
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@@ -3946,81 +3946,86 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
// before we compact, can we merge with our siblings?
lfsr_rbyd_t sibling;
for (uint8_t i = 0; i < 2; i++) {
lfs_ssize_t sibling_rid;
// try the right sibling
if (i == 0) {
sibling_rid = rid+1;
if ((lfs_size_t)estimate <= lfs->cfg->block_size/4
// no parent? can't merge
&& rid != -1) {
for (uint8_t i = 0; i < 2; i++) {
lfs_ssize_t sibling_rid;
// try the right sibling
if (i == 0) {
sibling_rid = rid+1;
// no right sibling? can't merge
if (sibling_rid >= (lfs_ssize_t)parent.weight) {
continue;
}
// try the left sibling
} else {
sibling_rid = rid-rbyd.weight;
}
// no parent? no sibling?
if (rid == -1
|| sibling_rid < 0
|| sibling_rid >= (lfs_ssize_t)parent.weight) {
continue;
}
// try looking up the sibling
// TODO do we really need to fetch sibling_weight if we get
// it in our btree struct?
lfsr_tag_t sibling_tag;
lfs_size_t sibling_weight;
lfsr_data_t sibling_data;
err = lfsr_rbyd_lookupnext(lfs, &parent,
sibling_rid, LFSR_TAG_NAME,
&sibling_rid, &sibling_tag, &sibling_weight,
&sibling_data);
if (err) {
// no sibling? can't merge
if (err == LFS_ERR_NOENT) {
continue;
// try the left sibling
} else {
sibling_rid = rid-rbyd.weight;
// no left sibling? can't merge
if (sibling_rid < 0) {
continue;
}
}
return err;
}
if (sibling_tag == LFSR_TAG_NAME) {
err = lfsr_rbyd_lookup(lfs, &parent,
sibling_rid, LFSR_TAG_WIDE(STRUCT),
&sibling_tag, &sibling_data);
// try looking up the sibling
// TODO do we really need to fetch sibling_weight if we get
// it in our btree struct?
lfsr_tag_t sibling_tag;
lfs_size_t sibling_weight;
lfsr_data_t sibling_data;
err = lfsr_rbyd_lookupnext(lfs, &parent,
sibling_rid, LFSR_TAG_NAME,
&sibling_rid, &sibling_tag, &sibling_weight,
&sibling_data);
if (err) {
LFS_ASSERT(err != LFS_ERR_NOENT);
// no sibling? can't merge
if (err == LFS_ERR_NOENT) {
continue;
}
return err;
}
}
LFS_ASSERT(sibling_tag == LFSR_TAG_BRANCH);
err = lfsr_data_readbranch(lfs, &sibling_data, sibling_weight,
&sibling);
if (err) {
return err;
}
// estimate if our sibling will fit
lfs_ssize_t sibling_estimate = lfsr_rbyd_estimate(lfs,
&sibling, -1, -1,
NULL);
if (sibling_estimate < 0) {
return estimate;
}
// fits? try to merge
if ((lfs_size_t)(estimate + sibling_estimate)
< lfs->cfg->block_size/2) {
if (i == 1) {
// if we're merging our left sibling, swap our rbyds
// so our sibling is on the right
bid -= sibling.weight;
rid -= rbyd.weight;
rbyd_ = sibling;
sibling = rbyd;
rbyd = rbyd_;
if (sibling_tag == LFSR_TAG_NAME) {
err = lfsr_rbyd_lookup(lfs, &parent,
sibling_rid, LFSR_TAG_WIDE(STRUCT),
&sibling_tag, &sibling_data);
if (err) {
LFS_ASSERT(err != LFS_ERR_NOENT);
return err;
}
}
LFS_ASSERT(sibling_tag == LFSR_TAG_BRANCH);
err = lfsr_data_readbranch(lfs, &sibling_data, sibling_weight,
&sibling);
if (err) {
return err;
}
// estimate if our sibling will fit
lfs_ssize_t sibling_estimate = lfsr_rbyd_estimate(lfs,
&sibling, -1, -1,
NULL);
if (sibling_estimate < 0) {
return estimate;
}
// fits? try to merge
if ((lfs_size_t)(estimate + sibling_estimate)
< lfs->cfg->block_size/2) {
if (i == 1) {
// if we're merging our left sibling, swap our rbyds
// so our sibling is on the right
bid -= sibling.weight;
rid -= rbyd.weight;
rbyd_ = sibling;
sibling = rbyd;
rbyd = rbyd_;
}
goto merge;
}
goto merge;
}
}