On Thu, Feb 18, 2010 at 7:04 PM, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
> Magnus Hagander wrote:
>> O_DIRECT helps us when we're not going to read the file again, because
>> we don't waste cache on it. If we are, which is the case here, it
>> should be really bad for performance, since we actually have to do a
>> physical read.
>>
>> Incidentally, that should also apply to general WAL when archive_mdoe
>> is on. Do we optimize for that?
>
> Hmm, no we don't. We do take that into account so that we refrain from
> issuing posix_fadvice(DONTNEED) if archive_mode is on, but we don't
> disable O_DIRECT. Maybe we should..
Since the performance of WAL write is more important than that of WAL
archiving in general, that optimization might offer little benefit.
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
