Re: Performance increase with elevator=deadline

On Fri, 11 Apr 2008, Jeff wrote:
> Using 4 of these with a dataset of about 30GB across a few files (Machine has
> 8GB mem) I went from around 100 io/sec to 330 changing to noop.   Quite an
> improvement.  If you have a decent controller CFQ is not what you want.   I
> tried deadline as well and it was a touch slower.  The controller is a 3ware
> 9550sx with 4 disks in a raid10.

I ran Greg's fadvise test program a while back on a 12-disc array. The
three schedulers (deadline, noop, anticipatory) all performed pretty-much
the same, with the fourth (cfq, the default) being consistently slower.

> it also seems changing elevators on the fly works fine (echo schedulername >
> /sys/block/.../queue/scheduler  I admit I sat there flipping back and forth
> going "disk go fast.. disk go slow.. disk go fast... " :)

Oh Homer Simpson, your legacy lives on.

Matthew

--
I suppose some of you have done a Continuous Maths course. Yes? Continuous
Maths? <menacing stares from audience> Whoah, it was like that, was it!
                                        -- Computer Science Lecturer