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chore: improve performance of ClearInternal (#3863)

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Before:
`BM_Clear/elements:32000     418763 ns       418749 ns         9965`

After:
`BM_Clear/elements:32000     323252 ns       323239 ns        12790`

Signed-off-by: Roman Gershman <roman@dragonflydb.io>
This commit is contained in:
Roman Gershman 2024-10-04 14:26:25 +03:00 • committed by GitHub
parent 0f972a0ec6
commit 2e1d81ac80
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GPG key ID: B5690EEEBB952194
2 changed files with 60 additions and 11 deletions
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68
src/core/dense_set.cc
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@ -180,21 +180,34 @@ void* DenseSet::PopDataFront(DenseSet::ChainVectorIterator it) {
}
void DenseSet::ClearInternal() {
constexpr unsigned kArrLen = 32;
ClearItem arr[kArrLen];
unsigned len = 0;
for (auto it = entries_.begin(); it != entries_.end(); ++it) {
while (!it->IsEmpty()) {
bool has_ttl = it->HasTtl();
bool is_displ = it->IsDisplaced();
void* obj = PopDataFront(it);
int32_t delta = int32_t(BucketId(obj, 0)) - int32_t(it - entries_.begin());
if (is_displ) {
DCHECK(delta < 2 || delta > -2);
} else {
DCHECK_EQ(delta, 0);
}
ObjDelete(obj, has_ttl);
if (it->IsEmpty())
continue;
DensePtr ptr = *it;
auto& dest = arr[len++];
dest.has_ttl = ptr.HasTtl();
PREFETCH_READ(ptr.Raw());
if (ptr.IsObject()) {
dest.obj = ptr.Raw();
dest.ptr.Reset();
} else {
dest.ptr = ptr;
dest.obj = nullptr;
}
if (len == kArrLen) {
ClearBatch(kArrLen, arr);
len = 0;
}
}
ClearBatch(len, arr);
entries_.clear();
num_used_buckets_ = 0;
num_links_ = 0;
@ -255,6 +268,39 @@ void DenseSet::CloneBatch(unsigned len, CloneItem* items, DenseSet* other) const
}
}
void DenseSet::ClearBatch(unsigned len, ClearItem* items) {
while (len) {
unsigned dest_id = 0;
// we walk "len" linked lists in parallel, and prefetch their next, obj pointers
// before actually processing them.
for (unsigned i = 0; i < len; ++i) {
auto& src = items[i];
if (src.obj) {
ObjDelete(src.obj, src.has_ttl);
src.obj = nullptr;
}
if (src.ptr.IsEmpty())
continue;
if (src.ptr.IsObject()) {
ObjDelete(src.ptr.Raw(), src.has_ttl);
} else {
auto& dest = items[dest_id++];
DenseLinkKey* link = src.ptr.AsLink();
dest.obj = link->Raw();
dest.has_ttl = link->HasTtl();
dest.ptr = link->next;
PREFETCH_READ(dest.ptr.Raw());
PREFETCH_READ(dest.obj);
FreeLink(link);
}
}
// update the length of the batch for the next iteration.
len = dest_id;
}
}
bool DenseSet::NoItemBelongsBucket(uint32_t bid) const {
auto& entries = const_cast<DenseSet*>(this)->entries_;
DensePtr* curr = &entries[bid];