Re: often PREPARE can generate high load (and sometimes minutes long unavailability) - Mailing list pgsql-hackers

From Andres Freund
Subject Re: often PREPARE can generate high load (and sometimes minutes long unavailability)
Date
Msg-id 20140223203206.GB20412@awork2.anarazel.de
Whole thread Raw
In response to often PREPARE can generate high load (and sometimes minutes long unavailability)  (Pavel Stehule <pavel.stehule@gmail.com>)
Responses Re: often PREPARE can generate high load (and sometimes minutes long unavailability)  (Pavel Stehule <pavel.stehule@gmail.com>)
List 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



pgsql-hackers by date:

Previous
From: Andres Freund
Date:
Subject: Re: Should PostgresMain() do a LWLockReleaseAll()?
Next
From: Marko Kreen
Date:
Subject: Re: SSL: better default ciphersuite