Re: RAID-0 read perf. decrease after 2.4.20

[Martin Knoblauch]

--- Marcelo Tosatti <marcelo.tosatti@xxxxxxxxxxxx> wrote:
> 
> 
> On Tue, 16 Dec 2003, Martin Knoblauch wrote:
> 
> > On Monday 08 December 2003 13:47, Marcelo Tosatti wrote:
> > 
> > Hi Marcelo,
> > 
> > > 2.4.20-aa included rmap and some VM modifications most notably
> > > "drop_behind()" logic which I believe should be the reason for
> the
> > huge
> > > read speedups. Can you please try it? Against 2.4.23.
> > 
> >  Just some feedback:
> > 
> > echo 511 > /proc/sys/vm/max-readahead
> > 
> >  brings back the read performance of my 30 disks on 4 controller
> > LVM/RAID0.
> 
> Great.
> 

 Indeed :-) Just to clarify - the modification of max-readahead was
sufficient to "fix" the observed read performance degradation. I did
not apply (or reverse) anything on top of 2.4.22.

 Actually 255 would have been sufficient, 511 proved to be a small bit
better :-))

Martin

=====
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www:   http://www.knobisoft.de
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