| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: often PREPARE can generate high load (and sometimes minutes long unavailability) |
| Date: | 2014-02-23 20:32:06 |
| Message-ID: | 20140223203206.GB20412@awork2.anarazel.de |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On 2014-02-23 20:04:39 +0100, Pavel Stehule wrote:
> There is relative few very long ProcArrayLocks lwlocks
>
> This issue is very pathologic on fast computers with more than 8 CPU. This
> issue was detected after migration from 8.4 to 9.2. (but tested with same
> result on 9.0) I see it on devel 9.4 today actualized.
>
> When I moved PREPARE from cycle, then described issues is gone. But when I
> use a EXECUTE IMMEDIATELY, then the issue is back. So it looks it is
> related to planner, ...
In addition to the issue Jeff mentioned, I'd suggest trying the same
workload with repeatable read. That can do *wonders* because of the
reduced number of snapshots.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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