On 2020/04/12 2:35, Noah Misch wrote:
When WalSndCaughtUp, sleep only in WalSndWaitForWal().
Before sleeping, WalSndWaitForWal() sends a keepalive if MyWalSnd->write
< sentPtr. That is important in logical replication. When the latest
physical LSN yields no logical replication messages (a common case),
that keepalive elicits a reply, and processing the reply updates
pg_stat_replication.replay_lsn. WalSndLoop() lacks that; when
WalSndLoop() slept, replay_lsn advancement could stall until
wal_receiver_status_interval elapsed. This sometimes stalled
src/test/subscription/t/001_rep_changes.pl for up to 10s.
Since this commit, walsender started consuming CPU resource too much in my env.
wakeEvents = WL_LATCH_SET | WL_EXIT_ON_PM_DEATH |
WL_TIMEOUT |
- WL_SOCKET_READABLE;
+ WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE;
I wonder if this change caused WaitLatchOrSocket() in WalSndLoop() to wake up
frequently more than necessary.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
