[petsc-dev] Fwd: [Xlab] slow pagefault on KNC

[Barry Smith]

   Should we have a test like this in the PETSc benchmark directory?

   Barry


Begin forwarded message:

> From: Kazutomo Yoshii <kazutomo at mcs.anl.gov>
> Subject: [Xlab] slow pagefault on KNC
> Date: December 17, 2012 10:48:06 AM CST
> To: "xlab at cels.anl.gov" <xlab at cels.anl.gov>
> 
> Hi,
> 
> I noticed that pagefault is very slow on KNC.  It takes 850 usec
> while it takes ~1 usec on Xeon, so prefaulting 1GB of memory region
> takes 222 sec on KNC.
> 
> This may not impact a big app runs for hours and hours, but I guess
> this definitely affects short-lived processes or threads, which might
> make MIC less fascinating.
> 
> This could be a hardware problem(need to check Phi), a kernel bug,
> or maybe sage of SMP kernel on many-core.
> If this is the last case, it would be really interesting for me.
> 
> Attached a simple page fault benchmark.
> 
> - kaz
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