Re: Proposed LogWriter Scheme, WAS: Potential Large Performance

Curtis Faith wrote:
> > No question about that!  The sooner we can get stuff to the WAL buffers,
> > the more likely we will get some other transaction to do our fsync work.
> > Any ideas on how we can do that?
> 
> More like the sooner we get stuff out of the WAL buffers and into the
> disk's buffers whether by write or aio_write.

Does aio_write to write or write _and_ fsync()?

> It doesn't do any good to have information in the XLog unless it
> gets written to the disk buffers before they empty.

Just for clarification, we have two issues in this thread:
WAL memory buffers fill up, forcing WAL writemultiple commits at the same time force too many fsync's

I just wanted to throw that out.

> > I can't tell you how many aio/mmap/fancy feature discussions we have
> > had, and we obviously discuss them, but in the end, they end up being of
> > questionable value for the risk/complexity;  but, we keep talking,
> > hoping we are wrong or some good ideas come out of it.
> 
> I'm all in favor of keeping clean designs. I'm very pleased with how
> easy PostreSQL is to read and understand given how much it does.

Glad you see the situation we are in.  ;-)

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
Pennsylvania19073