Horton

Re: Improving connection scalability: GetSnapshotData()

Andres Freund <andres@anarazel.de>

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From: "Andres Freund" <andres@anarazel.de>
To: pgsql-hackers@lists.postgresql.org
Date: 2020-09-07T20:45:48Z
Lists: pgsql-hackers 
Hi,


On Mon, Sep 7, 2020, at 07:20, Konstantin Knizhnik wrote:
> >> And which pgbench database scale factor you have used?
> > 200
> >
> > Another thing you could try is to run 2-4 pgench instances in different
> > databases.
> I tried to reinitialize database with scale 200 but there was no 
> significant improvement in performance.

If you're replying to the last bit I am quoting, I was talking about having four databases with separate pbench tables etc. To see how much of it is procarray contention, and how much it is contention of common buffers etc.


> Attachments:
> * pgbench.svg

What numactl was used for this one?

Commits

  1. Try to unbreak 021_row_visibility.pl on mingw.

  2. Fix and test snapshot behavior on standby.

  3. Fix race condition in snapshot caching when 2PC is used.

  4. snapshot scalability: cache snapshots using a xact completion counter.

  5. Fix use of wrong index in ComputeXidHorizons().

  6. Make vacuum a bit more verbose to debug BF failure.

  7. snapshot scalability: Introduce dense array of in-progress xids.

  8. snapshot scalability: Move PGXACT->vacuumFlags to ProcGlobal->vacuumFlags.

  9. snapshot scalability: Move subxact info to ProcGlobal, remove PGXACT.

  10. snapshot scalability: Move PGXACT->xmin back to PGPROC.

  11. snapshot scalability: Don't compute global horizons while building snapshots.

  12. BRIN: Handle concurrent desummarization properly

  13. Track latest completed xid as a FullTransactionId.

  14. Rename VariableCacheData.nextFullXid to nextXid.

  15. snapshot scalability: Move delayChkpt from PGXACT to PGPROC.

  16. Report progress of CREATE INDEX operations