Hi, On 2017-03-09 13:47:35 +0100, Naytro Naytro wrote: > We are having some performance issues after we upgraded to newest > version of PostgreSQL, before it everything was fast and smooth. > > Upgrade was done by pg_upgrade from 9.4 directly do 9.6.1. Now we > upgraded to 9.6.2 with no improvement. > > Some information about our setup: Freebsd, Solaris (SmartOS), simple > master-slave using streaming replication.
Which node is on which of those, and where is the high load?
High load in only on slaves, FreeBSD (master+slave) and Solaris (only slaves)
> Problem: > Very high system CPU when master is streaming replication data, CPU > goes up to 77%. Only one process is generating this load, it's a > postgresql startup process. When I attached a truss to this process I > saw a lot o read calls with almost the same number of errors (EAGAIN).
Hm. Just to clarify: The load is on the *receiving* side, in the startup process? Because the load doesn't quite look that way...
Yes
> read(6,0x7fffffffa0c7,1) ERR#35 'Resource temporarily unavailable' > > Descriptor 6 is a pipe
That's presumably a latches internal pipe. Could you redo that truss/strace with timestamps attached? Does truss show signals received? The above profile would e.g. make a lot more sense if not. Is the wal receiver sending signals?
> Read call try to read one byte over and over, I looked up to source > code and I think this file is responsible for this behavior > src/backend/storage/ipc/latch.c. There was no such file in 9.4.
It was "just" moved (and expanded), used to be at src/backend/port/unix_latch.c.
There normally shouldn't be that much "latch traffic" in the startup process, we'd expect to block from within WaitForWALToBecomeAvailable().
Hm. Any chance you've configured a recovery_min_apply_delay? Although I'd expect more timestamp calls in that case.
