Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < - Mailing list pgsql-committers

From Andres Freund
Subject Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <
Date
Msg-id 20160413212356.uv4velailmivnihh@alap3.anarazel.de
Whole thread Raw
In response to Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <  (Kevin Grittner <kgrittn@gmail.com>)
Responses Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <  (Alexander Korotkov <a.korotkov@postgrespro.ru>)
List pgsql-committers
On 2016-04-13 16:05:25 -0500, Kevin Grittner wrote:
> OK, thanks.  I can't think of anything else to ask for at this
> point.  If you feel that you have enough to press for some
> particular course of action, go for it.

I think we, at the very least, need a clear proposal how to resolve the
scalability issue around OldSnapshotTimeMapLock in 9.6.  Personally I
think we shouldn't release with such a large regression due to a
performance oriented feature; but if we do, we need to be confident that
we can easily resolve it for 9.7. In contrast to the spinlock issue I
don't see an easy way unfortunately. Without such a plan it seems too
likely to go unfixed for a long time otherwise.


> Personally, I want to do some more investigation on those big
> machines.

Sounds good, especially around the regression with the feature disabled.


Andres


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