Re: postgresql latency & bgwriter not doing its job

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.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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