On Tuesday 29 December 2009 04:04:06 Michael Clemmons wrote:
> Maybe not crash out but in this situation.
> N=0
> while(N>=0):
> CREATE DATABASE new_db_N;
> Since the fsync is the part which takes the memory and time but is
> happening in the background want the fsyncs pile up in the background
> faster than can be run filling up the memory and stack.
> This is very likely a mistake on my part about how postgres/processes
The difference should not be visible outside the "CREATE DATABASE ..." at all.
Currently the process simplifiedly works like:
------------
for file in source directory:
copy_file(source/file, target/file);
fsync(target/file);
------------
I changed it to:
-------------
for file in source directory:
copy_file(source/file, target/file);
/*please dear kernel, write this out, but dont block*/
posix_fadvise(target/file, FADV_DONTNEED);
for file in source directory:
fsync(target/file);
-------------
If at any point in time there is not enough cache available to cache anything
copy_file() will just have to wait for the kernel to write out the data.
fsync() does not use memory itself.
Andres
