Re: postgresql latency & bgwriter not doing its job

On Wed, Aug 27, 2014 at 10:20 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2014-08-27 10:17:06 -0300, Claudio Freire wrote:
>> > I think a somewhat smarter version of the explicit flushes in the
>> > hack^Wpatch I posted nearby is going to more likely to be successful.
>>
>>
>> That path is "dangerous" (as in, may not work as intended) if the
>> filesystem doesn't properly understand range flushes (ehem, like
>> ext3).
>
> The sync_file_range(SYNC_FILE_RANGE_WRITE) I used isn't a operation
> guaranteeing durability. And - afaik - not implemented in a file system
> specific manner. It just initiates writeback for individual pages. It
> doesn't cause barrier, journal flushes or anything to be issued. That's
> still done by the fsync() later.
>
> The big disadvantage is that it's a OS specific solution, but I don't
> think we're going to find anything that isn't in this area.

I guess it should work then.