High load (25% system) on 6450, 1+1+1=3 ;-)
Matt_Domsch at Dell.com
Tue Mar 19 12:36:01 CST 2002
> > > I am running stock 2.4.17 on a 6450. I have recently
> upgraded to 4 CPUs,
How many did you have before?
> total used free shared buffers cached
> Mem: 3996696 3890456 106240 0 75036 3300428
> -/+ buffers/cache: 514992 3481704
> Swap: 530104 32792 497312
You've got nearly 4GB RAM. With the stock 2.4.17 kernel, you're going to
see a lot of bounce buffer usage, which could easily account for the
increased CPU utilization.
Essentially, memory between 1GB and 4GB that is used for I/O buffers, is
getting "bounced", that is, copied into memory between 0-1GB, then the I/O
happens, then that low memory copied back to the high memory. See, two
extra copies for every I/O. Not ideal, especially when the controller can
DMA to/from high memory directly, there shouldn't be the need for this
There's work being done at Red Hat and elsewhere to decrease the need for
bounce buffers, so your performance would increase. The
announced-but-not-yet-released Red Hat Linux Advanced Server product has
significant improvements in this area, and of course there's the whole block
I/O rewrite (bio) in the 2.5.x kernel series to look forward to.
There's also SMP scalability improvements (Ingo Molnar's O(1) scheduler)
happening in the kernel, so if you've recently gone from 1 to 4 CPUs, you'll
probably see performance improvements with work too.
Sr. Software Engineer
Dell Linux Solutions www.dell.com/linux
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