On Mon, 2009-07-06 at 17:54 +0900, Fujii Masao wrote:
> According to the result, using sync_file_range instead of fdatasync
> has little effect in the performance of postgres.
["...when flushing XLOG"]
Why did you think it would?
AFAICS the range of dirty pages will be restricted to a fairly tight
range anyway. The only difference between the two would indicate an OS
inefficiency. I don't see an opportunity for XLOG to be more efficient
by using a finer-grained API.
I think there is still a valid use for sync_file_range at checkpoint,
since the for some large tables this could reduce the number of pages
needing to be written at checkpoint time. That would help smooth out
larger writes.
-- Simon Riggs www.2ndQuadrant.comPostgreSQL Training, Services and Support