He should be using all the threads for this. Using one thread to fault a bunch of memory is a recipe for terrible performance all around.
On Mon, Dec 17, 2012 at 9:21 AM, Barry Smith <bsmith at mcs.anl.gov> wrote: > > 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 > [see attached file: > pftest.c]_______________________________________________ > > Xlab mailing list > > Xlab at lists.cels.anl.gov > > https://lists.cels.anl.gov/mailman/listinfo/xlab > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20121217/747850d2/attachment.html>
