On 06/11/2010 04:47 PM, Tom Lane wrote:
Stefan Kaltenbrunner<ste...@kaltenbrunner.cc> writes:
hmm not sure that is what fujii tried to say - I think his point was
that in the original case we would have serialized all the operations
(first write+sync on the master, network afterwards and write+sync on
the slave) and now we could try parallelizing by sending the wal before
we have synced locally.
Well, we're already not waiting for fsync, which is the slowest part.
If there's a performance problem, it may be because FADVISE_DONTNEED
disables kernel buffering so that we're forced to actually read the data
back from disk before sending it on down the wire.
hmm ok - but assuming sync rep we would end up with something like the
following(hypotetically assuming each operation takes 1 time unit):
originally:
write 1
sync 1
network 1
write 1
sync 1
total: 5
whereas in the new case we would basically have the write+sync compete
with network+write+sync in parallel(total 3 units) and we would only
have to wait for the slower of those two sets of operations instead of
the total time of both or am I missing something.
Stefan
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
