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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_sync.cpp
+40 -20
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@@ -39,14 +39,36 @@ int blockstore_impl_t::continue_sync(blockstore_op_t *op)
if (PRIV(op)->sync_state == SYNC_HAS_SMALL)
{
// No big writes, just fsync the journal
if (!disable_fsync)
int n_sqes = disable_fsync ? 0 : 1;
if (journal.sector_info[journal.cur_sector].dirty)
{
BS_SUBMIT_GET_SQE(sqe, data);
my_uring_prep_fsync(sqe, journal.fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
data->callback = cb;
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 0;
PRIV(op)->pending_ops = 1;
n_sqes++;
}
if (n_sqes > 0)
{
io_uring_sqe* sqes[n_sqes];
for (int i = 0; i < n_sqes; i++)
{
BS_SUBMIT_GET_SQE_DECL(sqes[i]);
}
int s = 0;
if (journal.sector_info[journal.cur_sector].dirty)
{
prepare_journal_sector_write(journal, journal.cur_sector, sqes[s++], cb);
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 1 + journal.cur_sector;
}
else
{
PRIV(op)->min_used_journal_sector = PRIV(op)->max_used_journal_sector = 0;
}
if (!disable_fsync)
{
ring_data_t *data = ((ring_data_t*)sqes[s]->user_data);
my_uring_prep_fsync(sqes[s++], journal.fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
data->callback = cb;
}
PRIV(op)->pending_ops = s;
PRIV(op)->sync_state = SYNC_JOURNAL_SYNC_SENT;
}
else
@@ -90,11 +112,20 @@ int blockstore_impl_t::continue_sync(blockstore_op_t *op)
// Prepare and submit journal entries
auto it = PRIV(op)->sync_big_writes.begin();
int s = 0, cur_sector = -1;
if ((JOURNAL_BLOCK_SIZE - journal.in_sector_pos) < sizeof(journal_entry_big_write) &&
journal.sector_info[journal.cur_sector].dirty)
{
if (cur_sector == -1)
PRIV(op)->min_used_journal_sector = 1 + journal.cur_sector;
cur_sector = journal.cur_sector;
prepare_journal_sector_write(journal, cur_sector, sqe[s++], cb);
}
while (it != PRIV(op)->sync_big_writes.end())
{
journal_entry_big_write *je = (journal_entry_big_write*)
prefill_single_journal_entry(journal, JE_BIG_WRITE, sizeof(journal_entry_big_write));
dirty_db[*it].journal_sector = journal.sector_info[journal.cur_sector].offset;
journal.sector_info[journal.cur_sector].dirty = false;
journal.used_sectors[journal.sector_info[journal.cur_sector].offset]++;
#ifdef BLOCKSTORE_DEBUG
printf("journal offset %lu is used by %lu:%lu v%lu\n", dirty_db[*it].journal_sector, it->oid.inode, it->oid.stripe, it->version);
@@ -112,7 +143,7 @@ int blockstore_impl_t::continue_sync(blockstore_op_t *op)
if (cur_sector == -1)
PRIV(op)->min_used_journal_sector = 1 + journal.cur_sector;
cur_sector = journal.cur_sector;
prepare_journal_sector_write(journal, sqe[s++], cb);
prepare_journal_sector_write(journal, cur_sector, sqe[s++], cb);
}
}
PRIV(op)->max_used_journal_sector = 1 + journal.cur_sector;
@@ -147,18 +178,7 @@ void blockstore_impl_t::handle_sync_event(ring_data_t *data, blockstore_op_t *op
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;
}
release_journal_sectors(op);
// Handle states
if (PRIV(op)->sync_state == SYNC_DATA_SYNC_SENT)
{