Yeah, it is quite surprising that Design#2 is worse than master. I
suspect there is something wrong going on with your Design#2 patch.
One area to check is whether apply worker is able to quickly assign
the new relations to tablesync workers. Note that currently after the
first time assigning the tables to workers, the apply worker may wait
before processing the next set of tables in the main loop of
LogicalRepApplyLoop(). The other minor point about design#2
implementation is that you may want to first assign the allocated
tablesync workers before trying to launch a new worker.
It's not actually worse than master all the time. It seems like it's just unreliable.
Here are some consecutive runs for both designs and master.
design#1 = 1621,527 ms, 1788,533 ms, 1645,618 ms, 1702,068 ms, 1745,753 ms
design#2 = 2089,077 ms, 1864,571 ms, 4574,799 ms, 5422,217 ms, 1905,944 ms
master = 2815,138 ms, 2481,954 ms , 2594,413 ms, 2620,690 ms, 2489,323 ms
And apply worker was not busy with applying anything during these experiments since there were not any writes to the publisher. I'm not sure how that would also affect the performance if there were any writes.
Thanks,