Re: Production comparison between 2.4.27 and 2.6.8.1

[Nick Piggin]

Massimo Cetra wrote:
> Nick Piggin wrote:
>
> > > #**********************************************
> > > It is my first experience with 2.6 branch kernels, because 
> >
> > i am trying 
> >
> > > to figure out if the tree is performing well to switch 
> >
> > everithing in 
> >
> > > production, so my ideas may be wrong...
> > >
> > > Raid tests may be faked because of the overhead caused by 
> >
> > md sync (and 
> >
> > > probably raid is better on 2.6). However it seems that libsata has 
> > > better performance on 2.4 (hdparm) xfs tests shows that 2.4 
> >
> > has better 
> >
> > > performance if compared to 2.6 and the difference, in my 
> >
> > opinion, is 
> >
> > > not linked on libsata better performance.
> > >
> > > What is your opinion ?
> > > What can I try to improve performance ?
> >
> > I wouldn't worry too much about hdparm measurements. If you 
> > want to test the streaming throughput of the disk, run dd 
> > if=big-file of=/dev/null or a large write+sync.
> >
> > Regarding your worse non-RAID XFS database results, try 
> > booting 2.6 with elevator=deadline and test again. If yes, 
> > are you using queueing (TCQ) on your disks?
>
>
>
> Tried even with 2.6.8.1-mm and 2.6.8.1-ck
> No performance improvement.
>
> > From Documentation/block/as-iosched.txt i read:
>
> #--------------------------------------
> Attention! Database servers, especially those using "TCQ" disks should
> investigate performance with the 'deadline' IO scheduler. Any system
> with high
> disk performance requirements should do so, in fact.
>
> If you see unusual performance characteristics of your disk systems, or
> you
> see big performance regressions versus the deadline scheduler, please
> email
> me. Database users don't bother unless you're willing to test a lot of
> patches
> from me ;) its a known issue.
> #--------------------------------------
>
> So it's probably known that 2.6 performance with databases and heavy HD
> access is an issue.
> I don't believe that 2.6.x tree is performing as well as 2.4.x(-lck) on
> server tasks.
>
> Is this issue being analyzed ?
> Should we hope in an improvement sometime?
> Or I'll have to use 2.4 to have good performance ?

You booted with elevator=deadline and things still didn't improve
though, correct? If so, then the problem should be found and fixed.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/