Re: [Firebird-devel] FB 2.1 64bit and memory usage ??

[Alex P. <pes...@ma...>]

On Wednesday 25 July 2007 17:30, Vlad Horsun wrote:
> > I know various db "vendors" support direct I/O as a db option
> > on Linux, using the current O_DIRECT implementation, but they
> > had to be careful in their code to avoid certain O_DIRECT
> > kernel bugs and race conditions.  For example, it seems mixing
> > O_DIRECT and non-O_DIRECT reads and writes on the same file
> > simultaneously may result in stale data reads or writes. The
> > workaround: don't do that!
>
>     posix_fadvise free from this drawback and not restrict us to use
> aligned memory buffers, right ?

But lucks one more important support - direct I/O from/to user space. I 
suggest we begin with O_DIRECT, and only in case it has serious problems try 
with posix_fadvise(). This is even more important taking into an account that 
2.4 kernels do not support posix_fadvise().