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WIP Only save MVCC copy when overwriting an object

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This commit is contained in:
Vitaliy Filippov
2025-11-23 19:07:43 +03:00
parent 393f9d6b6f
commit 66847653aa
3 changed files with 83 additions and 82 deletions
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src/blockstore/blockstore_heap.cpp
+38 -17
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@@ -853,26 +853,40 @@ void blockstore_heap_t::reshard(pool_id_t pool, uint32_t pg_count, uint32_t pg_s
};
}
heap_object_t *blockstore_heap_t::lock_and_read_entry(object_id oid, uint64_t & lsn)
heap_object_t *blockstore_heap_t::lock_and_read_entry(object_id oid, uint64_t & copy_id)
{
auto obj = read_entry(oid, NULL);
if (!obj)
{
return NULL;
}
lsn = obj->get_writes()->lsn;
auto & mvcc = object_mvcc[(heap_object_lsn_t){ .oid = oid, .lsn = lsn }];
mvcc.readers++;
if (mvcc.entry_copy)
auto mvcc_it = object_mvcc.lower_bound({ .oid = { .inode = oid.inode, .stripe = oid.stripe+1 }, .lsn = 0 });
copy_id = 1;
if (mvcc_it != object_mvcc.begin())
{
return mvcc.entry_copy;
mvcc_it--;
if (mvcc_it->first.oid == oid)
{
if (mvcc_it->second.entry_copy)
{
// Already modified, need to create another copy
copy_id = mvcc_it->first.lsn+1;
}
else
{
copy_id = mvcc_it->first.lsn;
mvcc_it->second.readers++;
return obj;
}
}
}
object_mvcc[(heap_object_lsn_t){ .oid = oid, .lsn = copy_id }] = (heap_object_mvcc_t){ .readers = 1 };
return obj;
}
heap_object_t *blockstore_heap_t::read_locked_entry(object_id oid, uint64_t lsn)
heap_object_t *blockstore_heap_t::read_locked_entry(object_id oid, uint64_t copy_id)
{
auto mvcc_it = object_mvcc.find((heap_object_lsn_t){ .oid = oid, .lsn = lsn });
auto mvcc_it = object_mvcc.find((heap_object_lsn_t){ .oid = oid, .lsn = copy_id });
if (mvcc_it == object_mvcc.end())
{
return NULL;
@@ -884,9 +898,9 @@ heap_object_t *blockstore_heap_t::read_locked_entry(object_id oid, uint64_t lsn)
return read_entry(oid, NULL);
}
bool blockstore_heap_t::unlock_entry(object_id oid, uint64_t lsn)
bool blockstore_heap_t::unlock_entry(object_id oid, uint64_t copy_id)
{
auto mvcc_it = object_mvcc.find((heap_object_lsn_t){ .oid = oid, .lsn = lsn });
auto mvcc_it = object_mvcc.find((heap_object_lsn_t){ .oid = oid, .lsn = copy_id });
if (mvcc_it == object_mvcc.end())
{
return false;
@@ -1266,13 +1280,20 @@ int blockstore_heap_t::add_object(object_id oid, heap_write_t *wr, uint32_t *mod
heap_object_t *blockstore_heap_t::mvcc_save_copy(heap_object_t *obj)
{
auto oid = (object_id){ .inode = obj->inode, .stripe = obj->stripe };
auto lsn = obj->get_writes()->lsn;
auto mvcc_it = object_mvcc.find((heap_object_lsn_t){ .oid = oid, .lsn = lsn });
if (mvcc_it == object_mvcc.end())
auto mvcc_it = object_mvcc.lower_bound({ .oid = { .inode = oid.inode, .stripe = oid.stripe+1 }, .lsn = 0 });
if (mvcc_it == object_mvcc.begin())
{
return NULL;
}
assert(!mvcc_it->second.entry_copy);
mvcc_it--;
if (mvcc_it->first.oid != oid)
{
return NULL;
}
if (mvcc_it->second.entry_copy)
{
return mvcc_it->second.entry_copy;
}
assert(obj->size == sizeof(heap_object_t));
uint32_t total_size = obj->size;
for (auto wr = obj->get_writes(); wr; wr = wr->next())
@@ -1361,8 +1382,8 @@ int blockstore_heap_t::update_object(uint32_t block_num, heap_object_t *obj, hea
{
*modified_block = block_num;
}
// Save a copy of the object
heap_object_t *obj_copy = mvcc_save_copy(obj);
// Save a copy of the object - only when overwriting
heap_object_t *obj_copy = is_overwrite ? mvcc_save_copy(obj) : NULL;
bool tracking_active = !!obj_copy;
if (!tracking_active)
{
@@ -1486,10 +1507,10 @@ int blockstore_heap_t::post_stabilize(object_id oid, uint64_t version, uint32_t
*before_compact_lsn = pre_wr->lsn;
}
// Save a copy of the object
mvcc_save_copy(obj);
if (unstable_big_wr && unstable_big_wr->next())
{
// Remove previous stable entry series
mvcc_save_copy(obj);
free_object_space(obj->inode, unstable_big_wr->next(), NULL);
add_used_space(block_num, -free_writes(unstable_big_wr->next(), NULL));
unstable_big_wr->next_pos = 0;