This is a patch for load distributed checkpoint discussed in
http://archives.postgresql.org/pgsql-hackers/2006-12/msg00337.php
Only write() calls are smoothed, fsync() are not.
Existing checkpoint method is called "immediate checkpoint" in the patch,
and the new method called "asynchronous checkpoint".
I'm working on more robust control of checkpoint progress. WAL are written
a lot just after checkpoints because of full-page-writes and decreases
gradually. Linear control seems to be not enough in some cases.
Comments, suggestions and testing are appreciated.
Regards,
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ITAGAKI Takahiro
NTT Open Source Software Center
