On 4/19/15 3:08 PM, Jim Nasby wrote:
> I do suspect your pgfree/s is very high though; putting 200k
pages/s on
> the free list seems like something's broken.
>
The system has constant and considerable load of small writes. The
pg_activity tool shows 300 IOPs sustained (it claims max IPs above
11000.) Postgres 9.3 had a comparable pgfree/s.
That leads me to a new theory... you may be running into problems
finding free buffers in the buffer pool. We need to have a buffer before
we can extend a relation, and if you have a lot of pressure on shared
buffers it can take quite a bit of CPU to find one. To make matters
worse, that search for a buffer takes place while holding the extension
lock.
Would you be able to get a stack trace of a backend that's holding an
extension lock? Or maybe perf would provide some insight.
BTW,
http://postgresql.org/message-id/flat/20150329185619.GA29062@xxxxxxxxxxxxxxxxx
has some useful info about this.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com
--
Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
