From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: logical decoding - GetOldestXmin |
Date: | 2012-12-14 03:40:36 |
Message-ID: | CAB7nPqSvyv1AsEFbopwQW6nb+7h8V7GdqqN=OfA3SzYiqEmfyA@mail.gmail.com |
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On Fri, Dec 14, 2012 at 2:29 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Thu, Dec 13, 2012 at 3:03 PM, Andres Freund <andres(at)2ndquadrant(dot)com>
> wrote:
> > It moves a computation of the sort of:
> >
> > result -= vacuum_defer_cleanup_age;
> > if (!TransactionIdIsNormal(result))
> > result = FirstNormalTransactionId;
> >
> > inside ProcArrayLock. But I can't really imagine that to be relevant...
>
> I can. Go look at some of the 9.2 optimizations around
> GetSnapshotData(). Those made a BIG difference under heavy
> concurrency and they were definitely micro-optimization. For example,
> the introduction of NormalTransactionIdPrecedes() was shockingly
> effective.
>
The two commits coming to my mind are:
- ed0b409 (Separate PGPROC into PGPROC and PGXACT)
- 0d76b60 (introduction of NormalTransactionIdPrecedes)
Those ones really improved concurrency performance.
--
Michael Paquier
http://michael.otacoo.com
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