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Do not overwrite same journal sector multiple times

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It doesn't reduce actual WA, but it reduces tail latency (Q=32, 10% / 50% / 90% / 99% / 99.95%):
- write: 766us/979us/1090us/1303us/1729us vs 1074us/1450us/2212us/3261us/4113us
- sync: 701us/881us/1188us/1762us/2540us vs 269us/955us/1663us/2638us/4146us
This commit is contained in:
Vitaliy Filippov
2020-01-15 02:53:01 +03:00
parent 111516381f
commit a3d3949dce
7 changed files with 163 additions and 91 deletions
Download Patch File Download Diff File Expand all files Collapse all files
blockstore_write.cpp
+78 -49
View File
@@ -137,7 +137,6 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
{
// Small (journaled) write
// First check if the journal has sufficient space
// FIXME Always two SQEs for now. Although it's possible to send 1 sometimes
blockstore_journal_check_t space_check(this);
if (unsynced_big_writes.size() && !space_check.check_available(op, unsynced_big_writes.size(), sizeof(journal_entry_big_write), 0)
|| !space_check.check_available(op, 1, sizeof(journal_entry_small_write), op->len + JOURNAL_STABILIZE_RESERVATION))
@@ -145,18 +144,34 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
return 0;
}
// There is sufficient space. Get SQE(s)
BS_SUBMIT_GET_ONLY_SQE(sqe1);
struct io_uring_sqe *sqe1 = NULL;
if ((JOURNAL_BLOCK_SIZE - journal.in_sector_pos) < sizeof(journal_entry_small_write) &&
journal.sector_info[journal.cur_sector].dirty)
{
// Write current journal sector only if it's dirty and full
BS_SUBMIT_GET_SQE_DECL(sqe1);
}
struct io_uring_sqe *sqe2 = NULL;
struct ring_data_t *data2 = NULL;
if (op->len > 0)
{
BS_SUBMIT_GET_SQE_DECL(sqe2);
data2 = ((ring_data_t*)sqe2->user_data);
}
// FIXME: Write journal sector here only if it is full. Otherwise, defer it until SYNC. This will help reduce WA
// Got SQEs. Prepare journal sector write
// Got SQEs. Prepare previous journal sector write if required
auto cb = [this, op](ring_data_t *data) { handle_write_event(data, op); };
if (sqe1)
{
prepare_journal_sector_write(journal, journal.cur_sector, sqe1, cb);
// FIXME rename to min/max _flushing
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 1 + journal.cur_sector;
PRIV(op)->pending_ops++;
}
else
{
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 0;
}
// Then pre-fill journal entry
journal_entry_small_write *je = (journal_entry_small_write*)
prefill_single_journal_entry(journal, JE_SMALL_WRITE, sizeof(struct journal_entry_small_write));
prefill_single_journal_entry(journal, JE_SMALL_WRITE, sizeof(journal_entry_small_write));
dirty_it->second.journal_sector = journal.sector_info[journal.cur_sector].offset;
journal.used_sectors[journal.sector_info[journal.cur_sector].offset]++;
#ifdef BLOCKSTORE_DEBUG
@@ -172,9 +187,6 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
je->crc32_data = crc32c(0, op->buf, op->len);
je->crc32 = je_crc32((journal_entry*)je);
journal.crc32_last = je->crc32;
auto cb = [this, op](ring_data_t *data) { handle_write_event(data, op); };
prepare_journal_sector_write(journal, sqe1, cb);
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 1 + journal.cur_sector;
if (op->len > 0)
{
// Prepare journal data write
@@ -183,28 +195,34 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
// Copy data
memcpy(journal.buffer + journal.next_free, op->buf, op->len);
}
ring_data_t *data2 = ((ring_data_t*)sqe2->user_data);
data2->iov = (struct iovec){ op->buf, op->len };
data2->callback = cb;
my_uring_prep_writev(
sqe2, journal.fd, &data2->iov, 1, journal.offset + journal.next_free
);
PRIV(op)->pending_ops = 2;
PRIV(op)->pending_ops++;
}
else
{
// Zero-length overwrite. Allowed to bump object version in EC placement groups without actually writing data
PRIV(op)->pending_ops = 1;
}
dirty_it->second.location = journal.next_free;
dirty_it->second.state = ST_J_SUBMITTED;
journal.next_free += op->len;
if (journal.next_free >= journal.len)
{
journal.next_free = JOURNAL_BLOCK_SIZE;
}
// Remember small write as unsynced
unsynced_small_writes.push_back((obj_ver_id){
.oid = op->oid,
.version = op->version,
});
if (!PRIV(op)->pending_ops)
{
ack_write(op);
}
}
return 1;
}
@@ -223,45 +241,56 @@ void blockstore_impl_t::handle_write_event(ring_data_t *data, blockstore_op_t *o
PRIV(op)->pending_ops--;
if (PRIV(op)->pending_ops == 0)
{
// Release used journal sectors
if (PRIV(op)->min_used_journal_sector > 0)
{
uint64_t s = PRIV(op)->min_used_journal_sector;
while (1)
{
journal.sector_info[s-1].usage_count--;
if (s == PRIV(op)->max_used_journal_sector)
break;
s = 1 + s % journal.sector_count;
}
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 0;
}
// Switch object state
auto & dirty_entry = dirty_db[(obj_ver_id){
.oid = op->oid,
.version = op->version,
}];
#ifdef BLOCKSTORE_DEBUG
printf("Ack write %lu:%lu v%lu = %d\n", op->oid.inode, op->oid.stripe, op->version, dirty_entry.state);
#endif
if (dirty_entry.state == ST_J_SUBMITTED)
{
dirty_entry.state = ST_J_WRITTEN;
}
else if (dirty_entry.state == ST_D_SUBMITTED)
{
dirty_entry.state = ST_D_WRITTEN;
}
else if (dirty_entry.state == ST_DEL_SUBMITTED)
{
dirty_entry.state = ST_DEL_WRITTEN;
}
// Acknowledge write without sync
op->retval = op->len;
FINISH_OP(op);
release_journal_sectors(op);
ack_write(op);
}
}
void blockstore_impl_t::release_journal_sectors(blockstore_op_t *op)
{
// Release used journal sectors
if (PRIV(op)->min_used_journal_sector > 0 &&
PRIV(op)->max_used_journal_sector > 0)
{
uint64_t s = PRIV(op)->min_used_journal_sector;
while (1)
{
journal.sector_info[s-1].usage_count--;
if (s == PRIV(op)->max_used_journal_sector)
break;
s = 1 + s % journal.sector_count;
}
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 0;
}
}
void blockstore_impl_t::ack_write(blockstore_op_t *op)
{
// Switch object state
auto & dirty_entry = dirty_db[(obj_ver_id){
.oid = op->oid,
.version = op->version,
}];
#ifdef BLOCKSTORE_DEBUG
printf("Ack write %lu:%lu v%lu = %d\n", op->oid.inode, op->oid.stripe, op->version, dirty_entry.state);
#endif
if (dirty_entry.state == ST_J_SUBMITTED)
{
dirty_entry.state = ST_J_WRITTEN;
}
else if (dirty_entry.state == ST_D_SUBMITTED)
{
dirty_entry.state = ST_D_WRITTEN;
}
else if (dirty_entry.state == ST_DEL_SUBMITTED)
{
dirty_entry.state = ST_DEL_WRITTEN;
}
// Acknowledge write without sync
op->retval = op->len;
FINISH_OP(op);
}
int blockstore_impl_t::dequeue_del(blockstore_op_t *op)
{
auto dirty_it = dirty_db.find((obj_ver_id){
@@ -287,7 +316,7 @@ int blockstore_impl_t::dequeue_del(blockstore_op_t *op)
je->crc32 = je_crc32((journal_entry*)je);
journal.crc32_last = je->crc32;
auto cb = [this, op](ring_data_t *data) { handle_write_event(data, op); };
prepare_journal_sector_write(journal, sqe, cb);
prepare_journal_sector_write(journal, journal.cur_sector, sqe, cb);
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 1 + journal.cur_sector;
PRIV(op)->pending_ops = 1;
dirty_it->second.state = ST_DEL_SUBMITTED;