sysbench / fileio - Linux vs. FreeBSD

[Attilio Rao]

2010/6/5 Kostik Belousov <kostikbel at gmail.com>
>
> On Sat, Jun 05, 2010 at 07:41:23PM +0200, Attilio Rao wrote:
> > 2010/6/5 Matthew Jacob <mj at feral.com>
> > >
> > > All of these tests have been apples vs. oranges for years.
> > >
> > > The following seems to be true, though:
> > >
> > > a) FreeBSD sequential write performance in UFS has always been less than optimal.
> > >
> > > b) Linux sequential write performance in just about any filesystem has always been "impressive". But that "impressive" has come at some not so obvious costs. First of all, Linux is probably the most aggressive cluster/write-behind OS I've even seen. You can suck down all available memory with writebehind using dd. This means that some stats are "impressive", and others are "painful". A desktop that becomes completely unresponsive while you're doing this dd is one personal outcome.
> > >
> > > Also, you have to be careful what you're asking for in comparing the two platforms, or any platforms for that matter. What do you want to optimize for? Apparent responsiveness as a desktop? A specific workload (nfs, cifs) that completes N quatloos per fortnight?
> >
> > Besides anything, I'm much more concerned about the loss of
> > performance within FreeBSD itself. I wouldn't expect a so high
> > pessimization when the number of threads increases (without
> > considering the big performance loss with the 8k blocksize, pretty
> > much reproducible). I'm trying to drive, privately, the tester to
> > pmc/lock profiling analysis in order to start collecting some useful
> > datas.
> Are the benchmarks create threads that write to the same file ?
> If yes, then this behaviour is well understood.

Actually I still don't know as I just sent an e-mail to the tester and
he didn't followup still.
However I'm not entirely sure this is a full bottleneck which may be
reconduit to missing of byte-range locking.
I want to dig more and better understand what's going on exactly.

Attilio


--
Peace can only be achieved by understanding - A. Einstein