Re: 9.4 regression

On Mon, Aug 19, 2013 at 09:27:57PM -0400, Stephen Frost wrote:
> * Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
> > I vote for adapting the patch to additionally zero out the file via
> > write(). In your tests that seemed to perform at least as good as the
> > old method... It also has the advantage that we can use it a littlebit
> > more as a testbed for possibly using it for heap extensions one day.
> > We're pretty early in the cycle, so I am not worried about this too much...
>
> I dunno, I'm pretty disappointed that this doesn't actually improve
> things. Just following this casually, it looks like it might be some
> kind of locking issue in the kernel that's causing it to be slower; or
> at least some code path that isn't exercise terribly much and therefore
> hasn't been given the love that it should.
>
> Definitely interested in what Ts'o says, but if we can't figure out why
> it's slower *without* writing out the zeros, I'd say we punt on this
> until Linux and the other OS folks improve the situation.

Agreed. Anyone with an affected kernel really can't be doing
performance tests right now, and that isn't good.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +