Re: checkpointer continuous flushing

On 2016-01-09 18:04:39 +0530, Amit Kapila wrote:
> On Thu, Jan 7, 2016 at 4:21 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> >
> > On 2016-01-07 11:27:13 +0100, Fabien COELHO wrote:
> > > I read your patch and I know what I want to try to have a small and
> simple
> > > fix. I must admit that I have not really understood in which condition
> the
> > > checkpointer would decide to close a file, but that does not mean that
> the
> > > potential issue should not be addressed.
> >
> > There's a trivial example: Consider three tablespaces and
> > max_files_per_process = 2. The balancing can easily cause three files
> > being flushed at the same time.
> >
>
> Won't the same thing can occur without patch in mdsync() and can't
> we handle it in same way? In particular, I am referring to below code:

I don't see how that's corresponding - the problem is that current
proposed infrastructure keeps a kernel level (or fd.c in my versio) fd
open in it's 'pending flushes' struct. But since that isn't associated
with fd.c opening/closing files that fd isn't very meaningful.

> mdsync()

That seems to address different issues.

Greetings,

Andres Freund