[Pvfs2-developers] kernel bug warning

Robert Latham robl at mcs.anl.gov
Fri Mar 24 11:19:33 EST 2006


On Fri, Mar 24, 2006 at 09:05:24AM +0100, Phil Carns wrote:
> I'm not sure exactly which kernels from kernel.org are affected, but we 
> ran into a serious problem on the 2.6 kernel that we were using in RHEL4 
> (2.6.9-22.0.1.ELsmp).  The symptoms occur during a write-heavy 
> workloads.  From the PVFS2 point of view, write throughput on one or 
> more servers will slow to just a few KB/s, and the AIO thread will 
> consume 99% of cpu time.

Ugh.  Thanks for tracking this down.  I guess the only thing we can do
is add it to the FAQ?  
 
> David Metheny and I spent a long time tracking this down.  I highly 
> recommend oprofile for debugging performance bugs like this.  That was 
> what finally clued us in to where the problem was after a variety of 
> wrong turns :)

Glad to hear oprofile paid off!  

==rob

-- 
Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Labs, IL USA                B29D F333 664A 4280 315B


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