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Reverted multiple fetches of parents, other btree tweaks

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While it may make more logical sense to fetch the parent after our rbyd
commit completes, fetching the parent first just works out better in
terms of code deduplication.

            code          stack
  before:  20750           1752
  after:   20634 (-0.6%)   1744 (-0.5%)
This commit is contained in:
Christopher Haster
2023-08-15 22:56:50 -05:00
parent a2b8f81fc5
commit 842b143c91
1 changed files with 27 additions and 34 deletions
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lfs.c
+27 -34
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@@ -3913,6 +3913,18 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
// tail-recursively commit to btree
while (true) {
// we will always need our parent, so go ahead and find it
lfsr_rbyd_t parent;
lfs_ssize_t prid;
int err = lfsr_btree_parent(lfs, btree, bid, &rbyd, &parent, &prid);
if (err && err != LFS_ERR_NOENT) {
return err;
}
if (err == LFS_ERR_NOENT) {
// mark prid as -1 if we have no parent
prid = -1;
}
// fetch our rbyd so we can mutate it
//
// note that some paths lead this to being a newly allocated rbyd,
@@ -3921,19 +3933,17 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
//
// a funny benefit is we cache the root of our btree this way
if (!lfsr_rbyd_isfetched(&rbyd)) {
int err = lfsr_rbyd_fetch(lfs, &rbyd, rbyd.block, rbyd.trunk);
err = lfsr_rbyd_fetch(lfs, &rbyd, rbyd.block, rbyd.trunk);
if (err) {
return err;
}
}
// make a copy so we have a reference to the old trunk in case of split
lfsr_rbyd_t rbyd_ = rbyd;
// is rbyd erased? can we sneak our commit into any remaining
// erased bytes? note that the btree trunk field prevents this from
// interacting with other references to the rbyd
int err = lfsr_rbyd_appendall(lfs, &rbyd_, bid, -1, -1,
lfsr_rbyd_t rbyd_ = rbyd;
err = lfsr_rbyd_appendall(lfs, &rbyd_, bid, -1, -1,
attrs, attr_count);
if (err && err != LFS_ERR_RANGE) {
// TODO wait should we also move if there is corruption here?
@@ -4014,15 +4024,8 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
commit_recurse:;
// find our parent
lfsr_rbyd_t parent;
lfs_ssize_t prid;
err = lfsr_btree_parent(lfs, btree, bid, &rbyd, &parent, &prid);
if (err && err != LFS_ERR_NOENT) {
return err;
}
// no parent? we must be done
if (err == LFS_ERR_NOENT) {
// done?
if (prid == -1) {
LFS_ASSERT(bid == 0);
btree->u.r.rbyd = rbyd_;
return 0;
@@ -4034,6 +4037,9 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
return scratch_dsize;
}
// TODO can split and merge both end up with zero weight rbyds
// as well? do our tests cover this?
// prepare commit to parent, tail recursing upwards
//
// note that since we defer merges to compaction time, we can
@@ -4146,39 +4152,31 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
return scratch2_dsize;
}
// find our parent
err = lfsr_btree_parent(lfs, btree, bid, &rbyd, &parent, &prid);
if (err && err != LFS_ERR_NOENT) {
return err;
}
lfs_size_t pweight = rbyd.weight;
// no parent? introduce a new root
if (err == LFS_ERR_NOENT) {
if (prid == -1) {
int err = lfsr_rbyd_alloc(lfs, &parent);
if (err) {
return err;
}
// prepare commit to parent, tail recursing upwards
LFS_ASSERT(bid == 0);
prid = -1;
pweight = 0;
rbyd.weight = 0;
}
// prepare commit to parent, tail recursing upwards
bid -= prid - (pweight-1);
bid -= prid - (rbyd.weight-1);
scratch_attrs[0] = LFSR_ATTR(
bid+prid, BRANCH, 0,
BUF(scratch1_buf, scratch1_dsize));
scratch_attrs[1] = LFSR_ATTR(
bid+prid, GROW(RM), +rbyd_.weight-pweight,
bid+prid, GROW(RM), +rbyd_.weight-rbyd.weight,
NULL);
scratch_attrs[2] = LFSR_ATTR(
bid+prid+rbyd_.weight-(pweight-1), BRANCH, +sibling.weight,
bid+prid+rbyd_.weight-(rbyd.weight-1), BRANCH, +sibling.weight,
BUF(scratch2_buf, scratch2_dsize));
scratch_attrs[3] = (lfsr_tag_suptype(stag) == LFSR_TAG_NAME
? LFSR_ATTR(
bid+prid+rbyd_.weight-(pweight-1)+sibling.weight-1,
bid+prid+rbyd_.weight-(rbyd.weight-1)+sibling.weight-1,
BNAME, 0, DATA(sdata))
: LFSR_ATTR_NOOP);
attrs = scratch_attrs;
@@ -4188,13 +4186,8 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
continue;
merge:;
// find our parent
err = lfsr_btree_parent(lfs, btree, bid, &rbyd, &parent, &prid);
if (err && err != LFS_ERR_NOENT) {
return err;
}
// no parent? can't merge
if (err == LFS_ERR_NOENT) {
if (prid == -1) {
goto merge_abort;
}