Hi Sawada-san,
Thank you for your reply.
> Not sure but it might be possible to keep holding an xlogreader for
> reading PREPARE WAL records even after the transaction commit. But I
> wonder how much open() for wal segment file accounts for the total
> execution time of 2PC. 2PC requires 2 network round trips for each
> participant. For example, if it took 500ms in total, we would not get
> benefits much from the point of view of 2PC performance even if we
> improved it from 14ms to 1ms.
I made the patch based on your advice and re-run the test on the new machine.
(The attached patch is just for test purpose.)
* foreign_twophase_commit = disabled
2686tps
* foreign_twophase_commit = required (It is necessary to set -R ${RATE} as
Ikeda-san said)
311tps
* foreign_twophase_commit = required with attached patch (It is not necessary
to set -R ${RATE})
2057tps
This indicate that if we can reduce the number of times to open() wal segment
file during "COMMIT PREPARED", the performance can be improved.
This patch can skip closing wal segment file, but I don't know when we should
close.
One idea is to close when the wal segment file is recycled, but it seems
difficult for backend process to do so.
BTW, in previous discussion, "Send COMMIT PREPARED remote servers in bulk" is
proposed.
I imagined the new SQL interface like "COMMIT PREPARED 'prep_1', 'prep_2', ...
'prep_n'".
If we can open wal segment file during bulk COMMIT PREPARED, we can not only
reduce the times of communication, but also reduce the times of open() wal
segment file.
Regards,
Ryohei Takahashi
Hold_xlogreader.patch
Description: Hold_xlogreader.patch
