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

From Jeff Janes
Subject Re: often PREPARE can generate high load (and sometimes minutes long unavailability)
Date
Msg-id CAMkU=1zLY=dHyoeQ5jRUwJ=jOK_iw7J5oPFzp_5bc1wHmNz41g@mail.gmail.com
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In response to Re: 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)
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On Mon, Feb 24, 2014 at 7:02 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote:



2014-02-23 21:32 GMT+01:00 Andres Freund <andres@2ndquadrant.com>:

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.


I tested it, and it doesn't help.

Is there some patch, that I can test related to this issue?

This is the one that I was referring to:


Cheers,

Jeff


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