Re: Speedup twophase transactions

On Wed, Dec 9, 2015 at 12:44 PM, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru> wrote:

> Now 2PC in postgres does following:
> * on prepare 2pc data (subxacts, commitrels, abortrels, invalmsgs) saved to xlog and to file, but file not is not fsynced
> * on commit backend reads data from file
> * if checkpoint occurs before commit, then files are fsynced during checkpoint
> * if case of crash replay will move data from xlog to files
>
> In this patch I’ve changed this procedures to following:
> * on prepare backend writes data only to xlog and store pointer to the start of the xlog record
> * if commit occurs before checkpoint then backend reads data from xlog by this pointer
> * on checkpoint 2pc data copied to files and fsynced
> * if commit happens after checkpoint then backend reads files
> * in case of crash replay will move data from xlog to files (as it was before patch)

That sounds like a very good plan to me.

> Now results of benchmark are following (dual 6-core xeon server):
>
> Current master without 2PC: ~42 ktps
> Current master with 2PC: ~22 ktps
> Current master with 2PC: ~36 ktps

I assume that last one should have been *Patched master with 2PC"?

Please add this to the January CommitFest.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
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