Re: Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)

On Saturday 06 February 2010 06:03:30 Greg Smith wrote:
> Andres Freund wrote:
> > On 02/03/10 14:42, Robert Haas wrote:
> >> Well, maybe we should start with a discussion of what kernel calls
> >> you're aware of on different platforms and then we could try to put an
> >> API around it.
> >
> > In linux there is sync_file_range. On newer Posixish systems one can
> > emulate that with mmap() and msync() (in batches obviously).
> >
> > No idea about windows.
> The effective_io_concurrency feature had proof of concept test programs
> that worked using AIO, but actually following through on that
> implementation would require a major restructuring of how the database
> interacts with the OS in terms of reads and writes of blocks.  It looks
> to me like doing something similar to sync_file_range on Windows would
> be similarly difficult.
Looking a bit arround it seems one could achieve something approximediately
similar to pg_prepare_fsync() by using
CreateFileMapping && MapViewOfFile && FlushViewOfFile

If I understand it correctly that will flush, but not wait. Unfortunately you
cant event make it wait, so its not possible to implement sync_file_range or
similar fully.

Andres