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Fix and improve parallel allocation 

- Do not try to allocate more DB blocks in an inode block until it's "confirmed" and "locked" by the first write
- Do not recheck for new zero DB blocks on first write into an inode block - a CAS failure means someone else is already writing into it
- Throw new allocation blocks away regardless of whether the known_version is 0 on a CAS failure
master
Vitaliy Filippov 2023-11-29 01:32:09 +03:00
parent a64f0d1f73
commit 511bc3df1c
1 changed files with 126 additions and 39 deletions
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165
src/kv_db.cpp
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@ -123,6 +123,13 @@ struct kv_continue_write_t
std::function<void(int)> cb;
};
struct kv_alloc_block_t
{
uint64_t offset;
bool writing;
bool confirmed;
};
struct kv_db_t
{
cluster_client_t *cli = NULL;
@ -137,7 +144,7 @@ struct kv_db_t
uint64_t evict_unused_age = 1000;
uint64_t evict_max_misses = 10;
uint64_t evict_attempts_per_level = 3;
uint64_t allocate_blocks = 4;
uint64_t max_allocate_blocks = 4;
uint64_t log_level = 1;
// state
@ -146,7 +153,7 @@ struct kv_db_t
int base_block_level = 0;
int usage_counter = 1;
int allocating_block_pos = 0;
std::vector<uint64_t> allocating_blocks;
std::vector<kv_alloc_block_t> allocating_blocks;
std::set<uint64_t> block_levels;
std::map<uint64_t, kv_block_t> block_cache;
std::map<uint64_t, uint64_t> known_versions;
@ -160,6 +167,8 @@ struct kv_db_t
uint64_t alloc_block();
void clear_allocation_block(uint64_t offset);
void confirm_allocation_block(uint64_t offset);
void stop_writing_new(uint64_t offset);
void open(inode_t inode_id, json11::Json cfg, std::function<void(int)> cb);
void set_config(json11::Json cfg);
@ -539,7 +548,7 @@ void kv_db_t::set_config(json11::Json cfg)
this->evict_attempts_per_level = cfg["kv_evict_attempts_per_level"].is_null() ? 3 : cfg["kv_evict_attempts_per_level"].uint64_value();
this->evict_unused_age = cfg["kv_evict_unused_age"].is_null() ? 1000 : cfg["kv_evict_unused_age"].uint64_value();
this->cache_max_blocks = this->memory_limit / this->kv_block_size;
this->allocate_blocks = cfg["kv_allocate_blocks"].uint64_value() ? cfg["kv_allocate_blocks"].uint64_value() : 4;
this->max_allocate_blocks = cfg["kv_allocate_blocks"].uint64_value() ? cfg["kv_allocate_blocks"].uint64_value() : 4;
this->log_level = !cfg["kv_log_level"].is_null() ? cfg["kv_log_level"].uint64_value() : 1;
}
@ -567,49 +576,96 @@ void kv_db_t::close(std::function<void()> cb)
uint64_t kv_db_t::alloc_block()
{
// round robin between <allocate_blocks> blocks
while (allocating_blocks.size() < allocate_blocks)
// select from at least <max_allocate_blocks> allocation blocks
while (allocating_blocks.size() < max_allocate_blocks)
{
allocating_blocks.push_back(UINT64_MAX);
allocating_blocks.push_back({ .offset = UINT64_MAX });
}
if (allocating_blocks[allocating_block_pos] == UINT64_MAX)
bool found = false;
for (int i = 0; i < allocating_blocks.size(); i++)
{
// try v0 and only v0 of a new inode block
while (known_versions[next_free/ino_block_size] != 0)
int next = (allocating_block_pos+i) % allocating_blocks.size();
if (allocating_blocks[allocating_block_pos].offset != UINT64_MAX &&
allocating_blocks[next].confirmed && !allocating_blocks[next].writing)
{
next_free += ino_block_size;
allocating_block_pos = next;
found = true;
break;
}
allocating_blocks[allocating_block_pos] = next_free;
}
if (!found)
{
// Allow to allocate more new blocks in parallel than <max_allocate_blocks>
allocating_blocks.push_back({ .offset = UINT64_MAX });
allocating_block_pos = allocating_blocks.size()-1;
}
if (allocating_blocks[allocating_block_pos].offset == UINT64_MAX)
{
// allocate new blocks in the end
auto known_max = known_versions.end();
while (known_max != known_versions.begin())
{
known_max--;
// try v0 and only v0 of a new inode block
if (known_max->second != 0)
{
auto probably_unused = (known_max->first+1)*ino_block_size;
if (next_free < probably_unused)
next_free = probably_unused;
break;
}
}
allocating_blocks[allocating_block_pos] = {
.offset = next_free,
.writing = false,
.confirmed = false,
};
next_free += ino_block_size;
}
auto pos = allocating_blocks[allocating_block_pos];
allocating_blocks[allocating_block_pos] += kv_block_size;
if (!(allocating_blocks[allocating_block_pos] % ino_block_size))
auto pos = allocating_blocks[allocating_block_pos].offset;
allocating_blocks[allocating_block_pos].writing = true;
allocating_blocks[allocating_block_pos].offset += kv_block_size;
if (!(allocating_blocks[allocating_block_pos].offset % ino_block_size))
{
// Allow online reconfiguration
if (allocating_blocks.size() > allocate_blocks)
// Allow to reconfigure <max_allocate_blocks> online
if (allocating_blocks.size() > max_allocate_blocks)
allocating_blocks.erase(allocating_blocks.begin()+allocating_block_pos, allocating_blocks.begin()+allocating_block_pos+1);
else
allocating_blocks[allocating_block_pos] = UINT64_MAX;
allocating_blocks[allocating_block_pos].offset = UINT64_MAX;
}
allocating_block_pos = (allocating_block_pos+1) % allocating_blocks.size();
assert(block_cache.find(pos) == block_cache.end());
return pos;
}
void kv_db_t::clear_allocation_block(uint64_t offset)
{
// We want to be first when writing the first KV block into a new inode block
// After it other writers may modify already placed blocks and the version
// will increase, but they won't use free space in it for new blocks
if (known_versions[offset/ino_block_size] == 0)
for (int i = 0; i < allocating_blocks.size(); i++)
{
for (int i = 0; i < allocating_blocks.size(); i++)
if (allocating_blocks[i].offset/ino_block_size == offset/ino_block_size)
{
if (allocating_blocks[i]/ino_block_size == offset/ino_block_size)
{
allocating_blocks[i] = UINT64_MAX;
}
allocating_blocks[i].offset = UINT64_MAX;
}
}
}
void kv_db_t::confirm_allocation_block(uint64_t offset)
{
for (int i = 0; i < allocating_blocks.size(); i++)
{
if (allocating_blocks[i].offset/ino_block_size == offset/ino_block_size)
{
allocating_blocks[i].confirmed = true;
}
}
}
void kv_db_t::stop_writing_new(uint64_t offset)
{
for (int i = 0; i < allocating_blocks.size(); i++)
{
if (allocating_blocks[i].offset/ino_block_size == offset/ino_block_size)
{
allocating_blocks[i].writing = false;
}
}
}
@ -711,7 +767,10 @@ static void invalidate(kv_db_t *db, uint64_t offset, uint64_t version)
{
if (db->known_versions[offset/db->ino_block_size] < version)
{
db->clear_allocation_block(offset);
if (db->known_versions[offset/db->ino_block_size] == 0)
{
db->clear_allocation_block(offset);
}
auto b_it = db->block_cache.lower_bound(offset/db->ino_block_size * db->ino_block_size);
while (b_it != db->block_cache.end() && b_it->first/db->ino_block_size == offset/db->ino_block_size)
{
@ -1230,14 +1289,41 @@ static kv_block_t *create_new_block(kv_db_t *db, kv_block_t *old_blk, const std:
return blk;
}
static void write_new_block(kv_db_t *db, kv_block_t *blk, std::function<void(int, kv_block_t *)> cb);
static void place_again(kv_db_t *db, kv_block_t *blk, std::function<void(int, kv_block_t *)> cb)
{
auto old_offset = blk->offset;
auto new_offset = db->alloc_block();
del_block_level(db, blk);
std::swap(db->block_cache[new_offset], db->block_cache[old_offset]);
db->block_cache.erase(old_offset);
auto new_blk = &db->block_cache[new_offset];
new_blk->offset = new_offset;
new_blk->invalidated = false;
add_block_level(db, new_blk);
write_new_block(db, new_blk, cb);
}
static void write_new_block(kv_db_t *db, kv_block_t *blk, std::function<void(int, kv_block_t *)> cb)
{
write_block(db, blk, [=](int res)
{
db->stop_writing_new(blk->offset);
if (res == -EINTR)
{
// CAS failure => re-read, then, if not zero, find position again and retry
db->clear_allocation_block(blk->offset);
if (!(blk->offset % db->ino_block_size))
{
// Any failed write of the first block within an inode block
// means that someone else is already allocating blocks in it,
// so we HAVE to move to the next inode block immediately
db->clear_allocation_block(blk->offset);
place_again(db, blk, cb);
return;
}
// On the other hand, if the block is already "ours", then live parts
// of it may change and we MAY recheck if the block is still zero on CAS failure
cluster_op_t *op = new cluster_op_t;
op->opcode = OSD_OP_READ;
op->inode = db->inode_id;
@ -1264,16 +1350,7 @@ static void write_new_block(kv_db_t *db, kv_block_t *blk, std::function<void(int
else
{
// Block is already occupied => place again
auto old_offset = blk->offset;
auto new_offset = db->alloc_block();
del_block_level(db, blk);
std::swap(db->block_cache[new_offset], db->block_cache[old_offset]);
db->block_cache.erase(old_offset);
auto new_blk = &db->block_cache[new_offset];
new_blk->offset = new_offset;
new_blk->invalidated = false;
add_block_level(db, new_blk);
write_new_block(db, new_blk, cb);
place_again(db, blk, cb);
}
};
db->cli->execute(op);
@ -1281,6 +1358,7 @@ static void write_new_block(kv_db_t *db, kv_block_t *blk, std::function<void(int
else if (res != 0)
{
// Other failure => free the new unreferenced block and die
db->clear_allocation_block(blk->offset);
del_block_level(db, blk);
db->block_cache.erase(blk->offset);
cb(res > 0 ? -EIO : res, NULL);
@ -1288,6 +1366,12 @@ static void write_new_block(kv_db_t *db, kv_block_t *blk, std::function<void(int
else
{
// OK
if (!(blk->offset % db->ino_block_size))
{
// A successful first write into a new allocation block
// confirms that it's now "locked" by us
db->confirm_allocation_block(blk->offset);
}
cb(0, blk);
}
});
@ -1405,6 +1489,7 @@ void kv_op_t::create_root()
{
if (res == -EINTR)
{
db->clear_allocation_block(blk->offset);
auto blk_offset = blk->offset;
del_block_level(db, blk);
db->block_cache.erase(blk_offset);
@ -1413,6 +1498,8 @@ void kv_op_t::create_root()
}
else
{
db->stop_writing_new(blk->offset);
db->confirm_allocation_block(blk->offset);
db->stop_updating(blk);
finish(res);
}