On Wed, Feb 17, 2010 at 3:27 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> On Wed, Feb 17, 2010 at 06:55, Fujii Masao <masao.fujii@gmail.com> wrote:
>>> 2. Straightforwardly observe the alignment rule. Since the received WAL
>>> data might start at the middle of WAL block, walreceiver needs to keep
>>> the last half-written WAL block for alignment. OTOH since the received
>>> data might end at the middle of WAL block, walreceiver needs zero-padding.
>>> As a result, walreceiver writes the set of the last WAL block, received
>>> data and zero-padding.
>
>> May there be other reasons to d this as well?
>
> Writing misaligned data is certain to be expensive even when it works...
Yeah, right. After I remove O_DIRECT, I'll change walreceiver so as to
do an alignment correctly, and then I'll test the performance.
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
