Re: Poor DBT-3 pgsql 8way numbers on recent 2.6 mm kernels

[Ram Pai <linuxram@us.ibm.com>]

On Mon, 2004-03-15 at 08:45, Mary Edie Meredith wrote:
 
> 
> 
> > And if that is indeed the case I'd be suspecting the CPU scheduler.  But
> > then, Meredith's profiles show almost completely idle CPUs.
> > 
> > The simplest way to hunt this down is the old binary-search-through-the-patches process.  But that requires some test which takes just a few minutes.
> 
> If you are referring to a binary search to find when the
> performance changed, I can do this with STP.  It may take 
> some time, but I'm willing.  I didnt want to do that if 
> the problem was a known problem.  

Based on your data, I dont think readahead patch is responsible. However
since you are seeing this only on mm kernel there is a small needle of
suspicion on the readahead patch.

How about reverting only the readahaed patch in mm tree and trying it
out? 

http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.3-rc1/2.6.3-rc1-mm1/broken-out/adaptive-lazy-readahead.patch

My DSS workload benchmarks always touches the disk because I have only
4GB memory configured. I will give a try with 8GB memory and see if I
see any of your behavior. (I wont be able to put all my database in
memory)...

RP


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