Re: O_DIRECT please; Sybase 12.5

[Andrea Arcangeli]

On Fri, Jun 29, 2001 at 10:50:15AM +0100, Alan Cox wrote:
> > the boss say "If Linux makes Sybase go through the page cache on
> > reads, maybe we'll just have to switch to Solaris.  That's
> > a serious performance problem."
> 
> Thats something you'd have to benchmark. It depends on a very large number
> of factors including whether the database uses mmap, the average I/O size
> and the like

correct, here the benchmarks:

	http://boudicca.tux.org/hypermail/linux-kernel/2001week17/1175.html
        http://boudicca.tux.org/hypermail/linux-kernel/2001week17/att-1175/01-directio.png

of course the huge improvement is also because of broken VM in the
buffered-io case.

Andrea